Occasionally, when using Hotmail - specifically, putting the cursor into the email address box - the Mac color wheel starts spinning. This is quickly followed by the entire screen going black for a few moments. This is then followed by the screen returning, but the background screen saver changing from it's default to the blue that ordinarily appears temporarily when I boot up. This doesn't happen all the time, but it does occur. I visited the Apple Store "genius bar" and they checked out my machine. They cleaned up a few disc issues, and it still is happening. Their thought is that this is a Firefox issue, since they've not experienced it thus far, and it hasn't happened when I use hotmail with Google Chrome.