I don't think it's the game. I once got Resident Evil 4 and then all of a sudden my memory card messed up and couldn't save at all on any games. It's weird though since a few days later it worked again. I checked all the data I had (a few days before I deleted almost all of my games like you did to see if it was that) and there was a corrupted data box, then a few days later another without any problems happening.
Doesn't help solve your problem but I'm just saying, I don't think it matters on how old the game is since I got RE new.
Forgot to ask, have you tried saving on Deus Ex or does it only happen on Viewtiful Joe?