Also, when I try to search for a record, I receive this error:
"no records match this set of find requets" - even if the searched record exists.
Please, I really need some help on this probelm, ASAP.
In layout mode on tool bar under Layouts / Layout Setup make sure the correct table occurence is chosen in Show Records From
The error messages you are getting may indicate that your file is damaged or that an index is corrupted.
Make a recovered copy of the file. (launch filemaker without opening the file, choose recover from the file menu...)
Test the recovered copy to see if that fixes the problem.
If so, then replace your damaged file with an undamaged back up copy.