I attempted to install software to adjust the settings on the MS Wireless Mobile Mouse I'd plugged into the USB port. Prior to the install, everything had been going along smoothly - even the mouse - but after downloading and attempting to install the Mouse and Keyboard Center for the Mac, I started having problems.
First, simply clicking on the install package opened a dialog which said that the package could not be opened. After doing a Control-click (right-click on the MS mouse), it gave me the option to install, but nothing happened ... yet.
After two tries, I gave up ... and then found to my horror that when I attempted to run any other app (with or without the mouse plugged in), the app screen would flicker momentarily and then disappear. Restarting (with reopen windows checked first, then again with it unchecked) made no difference.
Now, I'm trying to shut the machine down and it wouldn't even do that unless I kept the power button pressed and forced a shutdown that way.
And yes, before you ask ... I'm going to go out and get an Apple mouse this weekend.