using the contrast rom and getting fragmentation error?
That means that your ROM is fragmented on your SD card.
If you are a Mac user, remove the ROM from the card and then recopy it back over.
If you are a Windows user, you have two options. Either use a program like Defraggler to defragment your SD card or take all of the files on your SD card off the card. Add your Pokemon ROM to the group, and then drag and drop them all back onto the card en masse.
I can't confirm the Windows method (seen other people say that it works.) I can confirm the Mac method though. That was one of the first issues that was brought up when Omega was released.