I tried pretty much everything with no solution. I have 3.40OE-A and I cant play ISO/CSO. I put an ISO in the correct ISO folder in root. I tried all the able/disable, NO UMD options in recovery. When I go to games and load from my MS it freezes and shuts down! I cant even see the ISO icon, it freezes before that!!! PLease HELP!!!!!! Thanks

hmm... is your memory stick is original??? same thing happened before to one of our co-members and he found out that his memory stick was a fake... if it's not fake, try to reinstall your firmware...

try and change your cpu speed to 333.... and make sure that you have a game loaded in the umd drive...

it can b da cso/iso ur using

I tried several different ISOs/CSOs with the same problem so I dont think its the ISOs I'm using. As far as the memory card, I have one 512MB which is real and I got a 4GB which is a fake but it has 38xxMB of memory and everything (emulators, movies,ROMS, pics, etc.) works fine so it cant be the MS!? I really weird how EVERYTHING else works except ISO. I can access the MS under camera, video, and music BUT as soon as I go into the game section its freezes and turns off. Is there a simple way to reinstall or do I have to downgrade and reinstall. Thanks

The downgrade then reinstall is safer.

You could try formatting the memory stick (remembering to back up your stuff first of course).

Alright I will try that, but how do I downgrade my 3.40OE-A. I started with with 2.71, then downgraded through a program to get to 1.50 then I upgraded to 3.40. Please tell me I DONT need lumines to do it!

You don't need Lumines.
Here is a guide on how to do it: http://www.psp-spot.com/forums/index.php?showtopic=41834
It says it's for semi-bricks, but as long as you can get to Recovery Mode it will work.
That should bring you back to 1.50, where you can install 3.40 OE-A again.