Thanks Mal after a long time I have RS working again

Paul (and any other vista users like me, I think this is the series of keystrokes needed in Vista)
Close RealSpeed
click on start (round icon extreme left bottom corner)
type in 'run' in the bottom left where it says 'start search' then hit enter
type in 'regedit' in the text box which appears, and click on ok
click on the small triangle beside 'HKEY_CURRENT_USER' (this opens the tree a bit more)
click on the small triangle beside Software
click on the small triangle beside Realspeed
click on the small triangle beside Grid fields
click on the small triangle beside Trackpoints
click on the word trackpoints and hit delete.
ok to any warning messages
Reopen Realspeed and mine now works having had the same error you had

Hope this works for you (getting RS working again makes me very happy anyway! Maybe the fact we are both on vista and have the same problem is a reflection on Vista)