David,

I found the problem with my combobox and thought I'd share it with you.
After checking all the properties I have overwritten and every single line of code I have associated with my form and the contained controls and objects, I still wasn't able to pinpoint the reason of the combobox's erratic behaviour. So out of desperation I started stripping my form of controls and stored procedures until eventually I was able to isolate the one line of code that doesn't seem to agree with the combobox.
It is: set delete on. Eventhough it makes no sense to me, getting rid of that line resolved my problem. If you have the time, try this and please let me know what you think.
Again, thanks a lot for your time and help.

Andrew