I have a problem where occasionally the start menu only opens with the top half showing, and it displays the top half where the bottom half would be, as if the entire menu has been shifted downwards, with the bottom actually below the bottom of the screen. It appears to be behind the taskbar, with the top of the task bar hiding all up to half-way up the 'Default programs' menu.
Apart from turning off the computer, the only way to fix it is to end the explorer process from the task manager and run it again as a new task.
I've found something which seems to trigger this error every time: pressing the arrow to view recent files from Adobe Reader 9. Every time I use this arrow, the next time I open the start menu, it has shifted down below my screen, without fail.
I'll upload photos if necessary but don't particularly like uploading screenshots of what I run.