Parallels Desktop 6 for Mac, prl_boot driver failed to start in Windows 7

Parallels Desktop 6 for Mac, Build 6.0.11826
Guest OS: Windows 7 x86/x64 (both)
Description:
This problem has been shown since upgraded from version 5 to 6:
Event ID 7026 has been logged after install parallels tools:

The following boot-start or system-start driver(s) failed to load: prl_boot

Re-install Parallels Tools doesn't resolve the issue. The description for this driver shown as "Boot Camp Helper". Does that mean if I don't have a boot camp partition, this error will always show in the windows event log? Is it safe to ignore this error?

Thanks

Chi

 

Windows Server 2008 R2 as well

The same issue occurs on my windows serevr 2008 R2 VM as well.