From the title, I have a 3.90 M33-3 PSP
I have tons of ISOS that have worked perfectly with no problems
However, it was all single player games God of War, FFVII: Crisis Core, Etc..
Just recently I tried to use the online multiplayer for Socom FTB and
when I select a match my psp will freeze up then turn itself off.
The same thing happened for Medal of Honor Heroes.

I had a FIFA 08 ISO once and the multiplayer mode did the same (turned off by itself) so I got another ISO of FIFA 08 and now the multiplayer mode works perfectly.

It's pretty weird that you encountered this problem with two games. Try another game but get it from a working source such as Demnoid. Use Mininova to search for the game.

what size are the games? are they at all ripped? because ripped games are not the best... which fireteam bravo game? 2 or 1, FTB2 ISO: should be in the 900 MB zone, CSO should be be around 650 MB? close to that, and medal of honor heroes I have a 489 MB CSO, and the ISO I have no clue... :P

To start, I got all of my games from pspiso and I've never had trouble from there.
Socom FTB 1 CSO - 115MB
Medal of Honor Heroes CSO- 186MB

So whoever ripped the games took the multiplayer out?
since they are compressed ISOS
...I guess they figured it was only for the single player aspect.

here's my advice never use ripped games... those more than half the time rarely work... and most of them have had the multiplayer ripped... look for bigger csos, csos are not ripped isos, but as you said just compressed... i believe I had the mohh cso size in my earlier post, and fireteam bravo 1, i can't help you there

What makes it a ripped game?
I'm not sure if these ones are, but I will remember
to look for bigger CSOs now if I plan on playing the mutliplayer

-thanks for the help

first off the size, and noticeable things missing...

EX, in Ratchet and Clank Size Matters, if you have a ripped game, the cut scenes are taken out, and are replaced with a logo, usually the EA Logo... it's annoying but it saves a lot of space, plus in the ripped Ratchet and Clank, multiplayer doesnt' work...

Another example, Rainbow Six Vegas, some of the guns models were ripped (don't know why, must've been ripped by a new person...) Plus in the single player, there is no sound...

Basically you can tell if a game is ripped just by playing it, watch for no sound, weird cut scenes, and no multiplayer (sometimes no single player...) Also do a size check, go through and find 2 or 3 DIFFERENT versions of a game's CSO/ISO, and look at their sizes, usually the bigger file is the one you want to get... note how I said usually, because I tried to find a good Vegas CSO, came in around 700 MB, wouldn't work. So look for those things, and check to see if it says RIPPED anywhere in the file name, thread or wherever.

alright, well I'll keep all of that in mind now
thanks again =]