Update: I can personally confirm “The IdolM@ster SP” does not boot on custom firmware 5.00 M33. It errors out with the following, “The game could not be started. (80020148).”

Furthermore, after doing a little research, it’s rumoured The Idolmaster SP will feature unlockable “PlayStation Home Rewards.” It’s likely 5.05 may accommodate that.

Uh oh… Apparently this new PSP title, The Idolmaster SP, comes bundled with PSP firmware version 5.05, and not only that, you absolutely need 5.05 to run it. It’s been reported, even with spoofing your firmware version, that for the moment Idolmaster SP does not work on any custom firmwares. So that begs the question: what’s up with firmware 5.05?

To quote Mr. Anonymous –

The series of THE iDOLM@STER SP games (japanese), released today but leaked earlier, comes with a new and neat 5.05 update that is pretty much required for the game to run, or, at least, does not work on any existing CFW at the time. Spoofing the version through version.txt seemingly doesn’t work, either.

- source: qj