Thanks for your reply John.
Yes I do have the latest FSUIPC (downloaded just a few days ago). I also seem to have (in addition to the above), a massive delay between instructions and keystroke options. For example ATC gives me take off clearance and no option to respond appears on the menu for sometimes up to a minute, maybe even more. This also happens when I respond or acknowledge. The voice response is extremely delayed.
I did have to re-install FSX a couple of weeks back due to atc.dll crashing the program all the time. Could that have something to do with the run time error?
Cheers.