What is going on with my computer? (Details follow)

I have a relatively new computer with Windows 7. For about a day now, when I am typing…the cursor will skip around, highlight and delete things, or move back two to three spaces when I am typing a word. Even when I slow down, the cursor will skip backwards to add my newly typed letters in the middle of the previous word. It is getting very tedious to type…arrrrgh!

This is what it looks like if I don’t correct the errors:

The quick be lazy poodle rown fox jumped over th

I have a virus program on the computer. Any ideas what is going on? It’s not the mouse as I adjusted that.

Help?