It appears this is happening due to the Action Replay corrupting the save.
I also had that problem when using Action Replay. My solution was, when you do the eprom backup it loads an evoX dashboard. While this is up you can use FlashFXP (a very sweet FTP program and well worth the money) to copy the save over to the Xbox into the UDATA folder. I had to unzip it first as the one I loaded into AR was zipped.
Just over write the one that was loaded by Action Replay. Then reboot and try it again. It worked great this way. The main thing is to get the game save over to where the Xbox will load it.
Now I have 4 modded Xboxes, 3 chipped and 1 soft modded. The soft mod is the coolest by far as I got it from Gamestop refurbished for $99. Considering the first modded xbox I spent $300 on, this is fabulotastic,