Trying to run MLB '06: The Show (UMD) on 1.5 Firmware

Hey all, sorry to be a bother. I've read a lot of the topics here about UMD loaders, and have tried several, but I have been unable to launch MLB '06: The Show on my PSP which has v1.5 firmware. So far I've tried RunUMD and Genesis UMD Launcher (which claims to work with all v2.6 games), but the same thing happens: I press O to extract the files, and then press X to launch the game, but instead of launching the game, my PSP just turns off. I tried both programs with GTA: Liberty City Stories, and it launches perfectly on both of them.

Is there any other loader out that I can try? I read about MPH's loader, but the tutorial started talking about ISOs and changing the prx file in a 2.xx iso and I wasn't sure what it was talking about. I'd rather play the game from the UMD than have to go out and spend more money on a memory stick (yes, I'm still using the stock 32 mb) so I can boot the ISO.

I was also thinking of just upgrading to v2.6 and using GTA to launch the homebrew stuff, but didn't want to actually do that until I knew for sure that would be better than running v1.5.

Sorry to sound like such a noob. Any help would be greatly appreciated. :D