Thanks to all for the helpful suggestions. I was able to resolve the problem but the answer was just as strange as the question... The code for my cmdSave.click() method originally looked something like this:

lcChanges = thisform.reportchanges()
select contracts
if tableupdate()
insert into audit values(...,...,lcChanges)

With things set up this way, the oldval()'s in 'thisform.reportchanges()' were already updated to the new values and therefore didn't think that anything had changed. All I did was move the select statement up one line and the problem went away...

select contracts
lcChanges = thisform.reportchanges()
if tableupdate()
insert into audit values(...,...,lcChanges)

Now I'm not quite sure why this would make a difference but, for whatever reason, it worked.