While working in Coherence view mode you can see video artifacts or glitches.
After Mac boots Parallels Desktop 6 for Mac crashes at the first start. Second start of Parallels Desktop is always successful.
Animation in Parallels Desktop 7 is enabled by the default in order to handle Lion OS X features. Some Windows applications' video behaviour may be affected or may conflict with Parallels Desktop animation solution.
In order to fix this issue Open Parallels Desktop Preferences → General → uncheck the 'Use animations' option.