Kinda difficult to comment without seeing the code that reads and writes to the EEPROM... really as Luciano states, create some simple code to write to EEPROM, then read it back and verify.

What I normally do, is also read the EEPROM back in my Programmer (always assumining your has that capability) and doubly confirm what I've written is actually stored there. That way you can concentrate on debugging the READ or the WRITE part of your code.

Of course you do have the latest PBP and MPLAB that has eliminated the internal EEPROM anomalies of the earlier versions?