Skipping cursor

My cursor will jump unexpectedly while I’m typing. I’m a touch typist so I don’t always watch the screen while I’m typing. All of a sudden I will be typing in the middle of 3 or 4 lines above where I expect to be. I have a Gateway laptop with a touch pad, I’m running XP Pro, but I also use a wireless Targus mouse.
Also sometimes the text will just disappear – be deleted and I can’t get it back so I have to re-type it all over. This happens in Word, Excel, Access and in my e-mail (Juno & GMail).
Any suggestions?