I also had this problem, but never having had any problems with any other game, and tried everything such as updating firmware to 4.41 rebug lite, rebuilding database, getting the game from another source, removing and reinstalling multiman and the only thing that worked for me was to Restore Default Settings in XMB.
Since then, no problems playing this amazing game, either with the original eboot or with 1.01 patch (I deleted the duplex one, it was just an intro that loads the original eboot, quite lame if you ask me).
I know it sound scary but - VERY IMPORTANT - make sure to select the correct option in XMB, it's under "System Settings" and it's called "Restore Default Settings" as that way you won't lose any precious savegames or trophies.
Just DON'T, repeat: DON'T select the option called "Restore PS3 System". IT'S NOT THAT ONE as that way you'll lose all your savegames, trophies and installed data, PSN games and homebrew! What you want is "Restore Default Settings". Got it? Good But if in doubt, just back everything up (I didn't need to do that and lost nothing).
More details: after selecting the option and restarting the PS3, I just did some minor fine tuning in the settings again, nothing special, to leave them like before. Why this was necessary? I suspect that some setting used on previous firmwares was still laying around and the game somehow got stuck on it.
My PS3 originally was a FAT 40 GB (Europe), I think originally with 2.x firmware and since then it had 3.41, 3.55, 3.55 kmeaw, a few Rogero and Rebug 4.x, and now is with Rebug 4.41 lite. The internal HDD was swapped to one with 320 GB but never was formatted except for the first time. Probably people with more recent consoles or that have formatted the HDD or resetted the settings since immemorial times are the ones not having problems with this game, that's my guess.
Hope I helped another soul, now go save humanity and lose some hours of sleep while getting delighted playing this