taskbar appears on start-up.......sometimes

All,

I run Win 7 32bit using Parallels 8 in Coherence mode. Every once in a while, when I start Windows, I get my Mac desktop, but the Windows' Taskbar appears. To remove the taskbar, I exit Coherence, wait while for the Windows' Desktop to appear, then exit that view and return to Coherence, and voila, the taskbar is gone.

This doesn't happen all the time. Does anyone know what might cause this?

thanks-

AF