So I've played what I think is most of the game (is there really a 15 level cap?) and the game glitches for me right after the battle with Craig, his clones, and cows in Clyde's tower. 

After I beat Craig, the game comes up with a weird screen that resembles the black loading screen, with either a chicken or a goth kid on the right and the word Loading underneath it.

It will flash my health, PP, & mana, on the top, and will also play all of the audio as if I'm back in the room and able to move. And if I swing my sword or walk around, I can hear the audio as if I was playing the part, but I cannot see anything but this weird loading screen. I've tried it multiple times, including getting a new game disc from Gamestop, and nothing changes it.

What I even tried to do was continue on through the door as if I was blind, to continue to the story, which I successfully did twice, but then it brings me to a cut scene, where all of the boys (excluding myself & Cartman who was my battle partner), Randy, and Mr. Slave are in a room together and then just nothing happens. 

This glitch is super frustrating because I've thoroughly enjoyed the game and I want to keep playing past it. 

Has this happened to other people? Is there a recommended solution? Any advice for me at all?

Yeah I'm having this problem too.

 

It sucks, I tried playing from earlier checkpoints as well but same end result.

 

I hope someone can shed some light or the guys at the game lab can send out a patch/update to fix it.

 

yeah i've got the same problem :/ hope they can get a fix out , I enjoying that game so much !