Jumping menus

[James41]

I wonder if you can suggest a solution to a problem I'm having with my display on XP. What happens is that when working on various programmes (none in particular) the Taskbar and Start menu jumps up and starts jumping around the screen. (On one occasion is re-arranged all my desktop items) It usually happens when I click the mouse to do something else but sometimes when I am not touching anything.
The only way I can gain control back is to press CRTL-Alt-Delete so that the task manager comes up. I then minimise that again and close the taskbar menu that has appeared and carry on. Sometimes though it has then altered the functions of the keys so that I cannot highlight a series of items when holding down the shift key. Only one item at a time can be used!
There can be hours of work sometimes before anything like that goes wrong but it seems more likely when I have several windows open and the internet connected.I was wondering if it was an unstable RAM problem.
Can you suggest anything else it might be please?
Many thanks,
James

[glc]

I'd try a different mouse and keyboard first.