I don't know of any specific problems with REBUG playing NHL 11. But I do know that myself and about 15 other people on these forums cannot play Uncharted 2 on REBUG at all. Only suggestion is maybe make sure the spoofer is not on in case its messing around with your PS3 recognizing the save data. Thats a long shot though, a wild guess at that...Only other suggestion I would give is flash Kmeaw and see if you have the same problem. Then you will know for sure that it is something either with REBUG or the REBUG settings.
As far as I know, my ps3 has never had an undetected error.