Disable Firmware Password Protection

I have a G4 Digital Audio. Since i installed a 1,7GHz procesor upgrade (Sonnet Encore) and had to apply a patch to the firmware it seems that open firmware password protection is enabled. Now i'm in trouble as i can't start up from a selected disk (i didn't consider it's on a > 128 GByte partition) and as i don't know the password (i haven't enabled it) i can't use the option key, so i can't startup the computer from any disk. Reading this: http://docs.info.apple.com/article.html?artnum=106482 i realized about the password protection and that there may be a way to bypass it having fisical access to the computer. Any hint what i can try to start up my computer again?