getting .iso/.cso 's to work on 3.03 OE-B

Having no luck playing any iso's or cso's on my psp.

I've tried no-umd mode, umd mode all that, but still no luck.
the games I've tried are MGS:po and Lumines, both show up fine in the os but when I click to play them i get the black screen then "game could not be started" error.

any help would be greatly appreciated. I'm not sure what I'm doing wrong, I've heard you can't have a "movie" umd in there.. but then I've heard it doesn't matter.. All I have is spider man2. I don't want to have to put devhook on 3.03 OE-B tog et this working as that would seem redundant.

I'm leaning towards the whole *can't use a movie umd" thing because I am hearing the umd engage before the error msg pops up...

Thank's in advance

thank's for the reply, and your right it shouldn't be here, guess I'm just used to posting here, my apologies.
yeah mgs:po was the first one I tried, then I dl'd lumines and that didn't work either so I'm assuming that's what the issue is. I'll jus borrow a game off my cousin and save $10 =D.
(yeah I'm a jerk)

I'll try that out and post the results see if it can't help someone else.