Some of you guys who are having issues after the update, did you delete the old _DS_MENU.SYS file when you updated?
That file is automatically created when running the new firmware the first time. If you didn't delete it before running the new one, it can cause all sorts of weird stuff to happen.
I don't know what that file does, but it needs to be re-written by the new firmware to work right. Make sure to leave at least 4 megs free for it, that's the size of the file.
Hope that's useful info to someone.