Definitely sounds like a virus. I'd try a different virus scanning package.

And when you ran Ad-Aware, did you run it to completion and let it remove everything? Not that adware would do that sort of thing, doesn't sound logical.

Another thing would be some kind of keyboard macro software. Do you have a programmable keyboard, or do you have any macro software loaded?

A final possibility is that your system has been compromised with a remote control back-door, and it's a hacker typing the words in "live".