I'm using build 1848 and this problem has occured for as long as I can remember. I typically have a cygwin window (like a DOS box) open in a Windows 2000 session. If I ever switch out of full screen mode with alt-enter and the cygwin window has focus, Parallels goes into its smaller window mode but now the cygwin window takes up the entire screen. Then if I make Parallels full screen the cygwin box takes up the entire screen but with the text area only occuping the middle part of the screen. The only way out of this is to exit from cygwin. If the cygwin window does not have focus when switching out of full screen mode everything is fine.
