Precision M60 - keyboard errors on certain keys

I have an M60 laptop, and recently it's started returning strange results:

h key returns H6

6 key returns H6

esc key returns '

- key returns '-

There may be others, but these are all I've noticed or remember so far.

This computer has never had internet access, it's a stand-alone work computer that runs a portable measuring device, so a virus is highly unlikely. I checked the keyboard regional settings, and everything looks ok. Any ideas on what to do? Thanks for any input!