Just updated to 5540. First attempt to start virtual machine with Vista, Parallels stated something about not being able to address the screen. Only option was to quit. Second attempt, and caused a system crash with the small multi-language window telling me to do a hard restart by holding down the power key 5 sec. Repeat attempt after rebooting, same result. Using Leopard. Previous version of Parallels (I do not recall the build #) worked fine in leopard.