Sometimes after I've been on the net a while, my AAO will freeze for no apparent reason-\- I can't do anything in the browser, can't get to the desktop or anything else. Can't close the browser. The red Quit button at the lower right of the screen won't work, and neither will the power switch on the key board. The only way I can turn the thing off is to disconnect the power cord and take out the battery. Then when I reconnect the power and restart, it's fine. Is this a common problem? Is there a simple fix?