Does the problem occur throughout the database? If not, if it's only in
a particular procedure or section of code, look for a place where you
execute the statement, "On Error Resume Next". That will keep error
messages from being displayed.
If it occurs throughout the database, I can't think of a reason except
that maybe the database or its VB project has become corrupt. In that
case, your problem might be solved by decompiling the database or, at
worst, creating a new database and importing all objects from the old
database into the new one.