help!!! jumping cursor

[taratata]

i am having the most frustrating problem!!! my cursor will just randomly "jump" from one spot to the next. it doesn't matter what program i'm working in. if i'm typing, the cursor will just jump to another spot...usually in the middle of one of my previous sentences. it will also sometimes highlight some or all of my text and if i don't notice in time and press the next key...there goes the text! if i'm writing an email, which i can't save as i go along, sometimes the whole body of the text will disappear - so a five minute email can turn into a painstaking half hour or so to write - or if i don't catch it, it sends partial emails. And I can't forget this part: when I sign in to something, it will jumble my whole email up over and over again, taking me forever to sign in - it's torture. Finally, the cursor has jumped around through this post, but I am finally finished!!! Please send help!!!!!