Arduino Mega 2560 Problem

Hi

I have an issue with my mega 2560.
We made a product based on a mega 2560

We already sold several but now i received some new arduino mega's

after i uploaded the code some don't work at all or give strange messages.
if i upload a older version of my code. the one without a lot of program memory entrys they do work. but to add the multilanguage option i add a lot of progmem items.

i checked my bootloaders with the ones who does work and i noticed the lockbyte is different.
the ones who work has a CF and the ones which do not work have a FF.
Can that be the problem and how can i change the ff back to CF

Kind regards

Johan

Please post your question on the Arduino forum:

http://arduino.cc/forum/

already did.
but thx already
i placed it under installation and troubleshooting
and then arduin 2560 problem