I've seen this on a few occasions.
Try the following until something works.
-- Open the VBA window and select Clear All Breakpoints from the debug menu
-- Open the Options (Tools: Options) and check the general tab options for
error breaks
-- Decompile your database and then compact
-- Now compile your code
You can use the decompile method to attempt a fix.
Check out the following:
http://www.mvps.org/access/bugs/bugs0008.htm
They are written for Access97 (the same method works for Access2000 and
Access2002, Access 2003).
Be sure to make a copy of your mdb before you decompile. I've never had any
trouble but ...
Last resort
-- create a new database and import everything into it.
John Spencer
Access MVP 2002-2005, 2007-2009
The Hilltop Institute
University of Maryland Baltimore County