Do you have a limit on how many records can be returned? Look for something like "parameter.maxrec=100" - maybe someone put a limit on how many records can be displayed. Since your problem recently appeared, that would be consistent with a limit being placed on what is returned. Doesn't mean that's the reason why, but is a good candidate for why it's happening now.
to check where the problem is lying ( database or frontend )
just create a new form with wizard . without changing any property . and without setting 1=1 in where clause .
then chech if it is fetching all records or not . if it is not retrieving all records and if it is fetching only after a certain date then we need to look un database end
else database end is fien check in teh forms end by copying these properties in ur actual form .