I recently installed Parallels Desktop 6 for Mac (build 6.0.11992) with a Windows 7 guest OS. In tracking down bad behavior in an application running under Windows (Quicken screen was refreshing once per minute for no reason, screwing up any typing I tried to do), I found in the Windows system log that every 60 seconds a time change event is being logged. Based on the registry values (which I left at the default) this should happen once per week, not once per minute. In all the events I've looked at, the old and new times are identical. If I modify the Windows startup so that the Parallels Tools service does not run, this problem does not happen. Re-enable the Parallels Tools service, problem starts again. I suspect this may be the root problem behind some of the "screen flicker" problems described in other threads. Even for apps that do not show visible problems there is a CPU usage spike that coincides with the time change events. Presumably Windows distributes this event to running applications, which react in various ways.
I find that if I turn off time sync to the Mac (Virtual Machine / Configure / Options / Advanced) the problem goes away. If there is a way to leave time sync enabled but have it done at a halfway reasonable frequency, I have not found it. I think this issue may be behind some of the performance problems noted in other threads. Even with just a couple of applications running, CPU usage would briefly spike to about 35% when the time change events happened every minute.
Known problem This is a known problem. We are working on it and hopefully it would be fixed in nearest update.
Mac Cloud Server has this problem Hello, I have a Mac Cloud Server hosted at GoDaddy. I am having this same issue, and I think it's also related to a kernel panic error that is causing GoDaddy to no longer offer the Mac Cloud Server to their customers. I noticed this because my QuickTime streaming server restarts frequently. It gives the cause as a system clock time change, happens from 5 to 30 minutes. I think if you fix this issue, you might be able to salvage the GoDaddy implementation. Just my take on this. I think if you can get control over the Xserve's time syncing, you'll have much fewer problems with the VMs running on that server.
