Laptop Weirdness

Ok, about 2 weeks after i got this lappy (E-machines m6805) i formatted with WinXP Pro. Everything went fine but the weirdest thing started happening, and even after this last format 2 days ago it is still happening. When i'm typing in aim,forums, irc, word doesn't matter where, with some sort of key combo (can't even duplicate it) my cursor will just re-locate itself to a random spot on the page and continuing typing!?! It's super annoying, thank god i don't have to reference the keyboard while i'm typing. What would cause this, i have tried hitting several key combos but to no avail. Just seems so weird to be typing and look up and your cursor is 4 lines up typing away. Never have had this problem with my pc's it's only present on the lappy..