"Unexpected Quit" problem solved, at least for me

Hi everyone, not sure if there is a generic known solution to the problem I'd like to label "unexpected quit". In any case, I couldn't find one searching the forums, but found many people having similar problems, so here are my 5 cent to the topic - to start with the result: In my configuration the problem is gone, at least for now (tested a few days):

* What's the Problem? Sometime after upgrading to 3.x my Parallels (beforehand rock solid) started showing fatal crashes that would materialize as sudden unexpected shutdowns of Parallels Desktop for Mac, sometimes with, but mostly without error message. The Guest OS Window, Or Coherence Window or Full Screen Window would simply vanish in the middle of whatever I was doing - even if I was doing nothing. No setting, operating mode, memory configuration etc. changed anything about that. The behaviour was also seemingly random - I was unable to nail a certain circumstance or state within the Guest OS to the crashes. Also the time before the first crash would vary drastically. From 15 minutes to 12 hours I would say.

* Route to solution: As I couldn't find a solution I tried to narrow the problem down. The only reasonable assumption I found on the net was that of a memory leak. I started looking there, using the following setup:

MB Pro Core 2 Duo, 2.33 GHz, 2GB RAM, Parallels Desktop 3.0 for Mac Build 5160, Windows XP with SP2 and all current patches in Window Mode

As many people reported problems with "Poker Apps", I tried the Pokerstars client as my test subject running in Windows with no other software running than XP drivers, Parallels tools and a security suite (Bitdefender 10).

VM Configuration: 512MB, Bridged Ethernet, USB connecting to Host. Memory Limit on Manual, 1024 MB, All Animations off (Last settings all in preferences)

I fired up Activity Monitor on the Mac, picked Parallels process by double clicking, selected Memory Tab, then booted the VM. After Boot I started using Pokerstars to play around and watched the memory inspection window.

The interesting value is "Real Memory Size" - sure enough, while it was changing up and down regularly, the average value slowly but constantly rose.

Playing around in Pokerstars then quickly revealed that functions requiring quick, multiple network accesses (such as bringing up all tables in a game category) would cause a larger memory drain then slower network accesses (such as playing a table with few players).

I then played around with network related services in WinXP and to make a long story short: in true Murphy's law fashion pretty much the last idea I had was to disable Bitdefender. Boom - Problem solved. Memory Footprint solid. No more crashes since than.

Why the long story? I can't believe that everyone having the problem is using bitdefender nor do I believe that the bug is necessarily caused by that software. But the approach above should allow people to find out if there is a software in their system they can disable to avoid the Memory Leak - I would guess that anything drastically increasing the system load in the guest os in the areas HD access and/or Network access will cause the symptoms to show. In many cases that would be Anti Virus Software with Real Time Protection and Scanning or Disk or File Encryption Software on a System level.

Cause: No clue, but I am willing to speculate: There must be a bug in the handling of some of the File System and/or Network access relevant DMA or IRQ handlers that leads to events being missed under heavy load causing data residue that is neither processed nor freed, stealing memory over time and eventually destroying relevant data structures used by parallels. Symptoms would be exactly as encountered with errors ranging from Division by Zero to Jumps into memory pages marked non-executable or garbled stacks.

Peace!