Unable to switch to Coherence

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Eric Hamburg

Junior Member
I'm getting this message when trying to switch from Full Screen to Coherence mode:

"Unable to switch to Coherence.
The virtual machine display configuration could not be applied. Please try again or contact Parallels Support ..."

I tried again but same error.

I looked at the Windows Device Manager and don't see anything flagged.

Running under OS X 10.6.5, Windows 7 Ultimate with 1GB allocated, Parallels 6.0.11828 on iMac 27" 8GB.

I've generally been running full screen and haven't tried Coherence for a long time so I don't know if this is an issue with the recent OS X 10.6.5 upgrade or not.

I'd really like to get Coherence working as I really hardly ever use Windows anymore but I would like to have the Oxford English Dictionary, which unfortunately is Windows only, running in a window at all times.
 
I have the same issue

I just started getting this yesterday.

Running under OS X 10.6.4, Windows 7 Home Premium with 2GB allocated, Parallels 6.0.11828 on MBP 15" 8GB.

I have not yet upgraded to OS X 10.6.5. I upgraded to Parallels 11828 a week or so ago, but have been using the VM since that time (up until yesterday) in coherence mode.

In a related post, it was recommended to reinstall Parallels Tools. I did this, but still can't get Win7 to change to coherence.

I have a second VM guest running Windows XP -- coherence works fine on that instance.
 
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Tested on my MBP - Coherence works

I tried to switch to Coherence on my MBP which was had not been updated to the most current rev of Parallels and was running 10.6.4 OS X. Switch to Coherence worked. I then updated Parallels to 11828 and OS X to 10.6.5. After updates Coherence still works on the MBP. So ... the problem I am having is isolated to my 27" iMac.
 
Can you set the virtual machine to have more RAM? If you're Mac has 8 GB of RAM, then giving the virtual machine 3 or 4 GB should be ok. Also make sure the Video settings in the virtual machine configuration is set to 256 MB.
 
Video was set to 256.

I first increased RAM 4 GB. Still won't switch to Coherence. BTW looking at memory in computer properties it says that only while 4 is allocated only 2.75 is available. I bumped it down to 2 GB. Still no go.

Additionally, I noticed while looking at properties that it said that the Windows Experience Index needed to be refreshed. This make sense as this VM was previously installed on a lower powered iMac that I have given to someone else. I ran the refresh, first running the VM at 2 GB RAM. The Index went from 4.1 to 5.3, but still no Coherence. I then bumped the RAM down to 1 GB, reran the Index which is now at 4.5. Still no Coherence.
 
Coherence started working again this morning. The only change is that I am using an external monitor today. I have not rebooted.
 
If I disconnect my external monitor by unplugging the mini display port adapter from the iMac and Coherence works. If the external monitor is connected the switch to Coherence fails as before either if the power to the external monitor is off and even if I have "remove(d) this display" from the Windows multiple monitor drop down.
 
Eric, sounds like you get the problem only when you are using multiple monitors?

Adam, you get the problem when you're only using the MBP's built in screen? When you're using an external monitor, is the built in display still being used (i.e. you're using multiple displays)? Does your MBP have the two graphics chips? Do you know which chip is being used for each display?

Does changing the "Use all displays in full screen" option at Virtual Machine -> Configure -> Options -> Full Screen affect this?

What about lowering the Video RAM from 256 MB to something like 128 MB or 64 MB?
 
My test have been with "Use all displays in full screen" unchecked. I toggled it on and it made no difference. Same error. Thanks.
 
Cannot replicate

Sorry, I cannot replicate the issue at this time.

Also, to answer your questions:

Adam, you get the problem when you're only using the MBP's built in screen? Yes
When you're using an external monitor, is the built in display still being used (i.e. you're using multiple displays)? Yes
Does your MBP have the two graphics chips? Yes
Do you know which chip is being used for each display? I am only using the base chip (9400M, not 9600M GT). I verified this in System Profiler.
 
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More coherence strangeness

Yesterday, I put the MBP to sleep and reopened it today.

Parallels came back with: "Unable to switch to Coherence. The Parallels mouse synchronization service is not started. Reinstall Parallels Tools and try again." Windows 7 then crashed and rebooted. The funny thing is, after Win-7 restarted, coherence works fine again without another reinstall of Parallels Tools.

The "Windows Recovered from an Unexpected Shutdown" window/dump details follow:

Problem signature:
Problem Event Name: BlueScreen
OS Version: 6.1.7600.2.0.0.768.3
Locale ID: 1033

Additional information about the problem:
BCCode: c2
BCP1: 00000007
BCP2: 00001097
BCP3: B80B6000
BCP4: 83BDD388
OS Version: 6_1_7600
Service Pack: 0_0
Product: 768_1

Files that help describe the problem:
C:\Windows\Minidump\111810-42656-01.dmp
C:\Users\adam\AppData\Local\Temp\WER-662375-0.sysdata.xml
 
it says: mouse synchronization service is not started, ...

Mine has the same problem.

MBP 10.6.5 (8G ram, with windows 7 guest OS applied to 2G ram, parallels 6.0.11990)

Parallels says: "Parallels mouse synchronization is not started. Reinstall Parallels Tools and try again.

So I reinstalled parallels several times and no success in vein. It still says that again and again.
 
You reinstalled Parallels Desktop or Parallels Tools?

To reinstall Parallels Tools, first run Windows and uninstall it using Add/Remove programs in Windows. Then reboot Windows. Then select "Install Parallels Tools" from From the Parallels Desktop Virtual Machine menu.
 
Status of this issue

After various communications with Parallels support and escalation to second level support this issue stands as follows, specifically with my iMac 27" set to 2560 X 1440 resolution and the secondary display connected to the iMac via a mini-display port adapter is set to 1920 X 1080.:

"it is one of the known issues recently discovered. Unfortunately, it is not fixed yet, but being investigated by the development team closely. The fix is most likely to be included in Parallels Desktop 7."
 
Unable to start Coherence Mode

I have two virtual machines: Windows 7 and Windows XP. Windows 7 works fine at the moment. Windows XP gives the message that it cannot start Coherence. Mouse synchronization is not started and a reinstall of Parallels Tools is requested. Reinstall does not fix the problem. I am running the 11828 version of Parallels after problems with later versions.
 
Success

I uninstalled Parallels Tools before reinstalling and this time it worked. Coherence is now operational. I wonder if this was some residual damage from before I backed up to Parallels release 11828.
 
This error happens now & then, and has to do with the imac27 with multi monitors. If there is any change in the monitor configuration on the Mac, I got this error... Sometimes a reboot works, sometimes not.

The problem is still here, on version 7
 
I saw this error today, on my 27" iMac. I have the main display and two other monitors attached to it. I was able to get the problem to go away by moving the Parallels window back over to the main iMac monitor. Once I did that, it entered Coherence mode just fine. Once there, I could move individual windows over to the other monitors without a problem.
 
Not here -- the case where I saw it was with Parallels 7, and I can reliably reproduce it. Every time I move the window off the main screen, Coherence fails to start. As soon as I move it back, it starts just fine.
 
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