hard to say, but I would __GUESS__ it might be a references problem of some kind.
When this happens, you need to take steps to let Access repair the broken
reference(s) ON THE COMPUTER WHERE THE FAILURE IS OCCURING.
Here are MVP Doug Steele's instructions for how to do it:
*** Quote ***
Any time functions that previously worked suddenly don't, the first thing to
suspect is a references problem.
This can be caused by differences in either the location or file version of
certain files between the machine where the application was developed, and where
it's being run (or the file missing completely from the target machine). Such
differences are common when new software is installed.
On the machine(s) where it's not working, open any code module (or open the
Debug Window, using Ctrl-G, provided you haven't selected the "keep debug window
on top" option). Select Tools | References from the menu bar. Examine all of the
selected references.
If any of the selected references have "MISSING:" in front of them, unselect
them, and back out of the dialog. If you really need the reference(s) you just
unselected (you can tell by doing a Compile All Modules), go back in and
reselect them.
If none have "MISSING:", select an additional reference at random, back out of
the dialog, then go back in and unselect the reference you just added. If that
doesn't solve the problem, try to unselect as many of the selected references as
you can (Access may not let you unselect them all), back out of the dialog, then
go back in and reselect the references you just unselected. (NOTE: write down
what the references are before you delete them, because they'll be in a
different order when you go back in)
For far more than you could ever want to know about this problem, check out
http://members.rogers.com/douglas.j.steele/AccessReferenceErrors.html
Just so you know: the problem will occur even if the library that contains the
specific function that's failing doesn't have a problem.
**** End Quote ****
So, follow those instructions and see if your problem goes away.
Check out the following reference
http://www.trigeminal.com/usenet/usenet026.asp?1036