Ok, this one seems weird. I just upgraded to Parallels 7 and created a new Lion guest. Everything went fine and I installed Parallels tools. I then ran the Software Update (in the guest Lion OS) and while it was "checking for new software", I switched to another Windows on the host machine (also running Lion) and I switched back to the guest Window and the "checking for new software" window immediately disappeared, like I had clicked the Cancel button, but I did not. I tested it a couple more times and every time I'd come back to the guest window, it would "click" the Cancel button. This happens no matter how I get back to the guest window. I can click on the Parallels title bar for the window, click inside the guest window, or just tab back to the guest window. All those actions "click" the Cancel button. I'm not sure why this is happening on this particular window (the Check for Updates window). It doesn't seem to happen with that many other windows. I just tested it a bit more and found that it seems to happen on "sheets" a lot (all the time?). For instance, if you go to System Preferences => Energy Saver and click the "Schedule..." button, a sheet opens to let you set the schedule. If you leave the guest window and come back, the sheet gets closed.