I though there's dozen of this kind of posts..
Well I have 3.71 M33-4 and i was told to only use that version. I do not understand why until now..
Since the newer M33 than 3.71 still have glitches on reading cso/iso from memory stick, even optional fixes can cause other side effects.. Older than 3.71 firmwares are not compatible with all new games which basically sux. So yeah im really happy with 3.71 M33-4, PSX games works, latest games works, no glitches.. Just good. But i hope D_A release stable M33 for 4.0 CFW in future. Since there will be need of newer kernal than 3.71 im sure of it..