XP: mouse control lost

In the last 2 days I have been experiencing a problem on my computer. After
startup the user loses the mouse control. the mouse goes by itself to the
start button a
keep sending mouse click. Sometimes it opens windows
and all the stuff. After a while it gives control to the user.
I tried Norton anti-virus and a couple of script cleaners but
nothing helps. Anyone seen this bug/script issue ...

Cheers,

Oufella