ahh g3 imac yaboot error, wont boot

i had shut down and everything just fine after a few reboots, and now my imac will not boot up, i type in l for linux or c for cd and nothign works. it just goes to yaboot prompt and says LOAD SIZE IS TOO SMALL and i can not boot from anything, someone plerase help me i was just starting to have fun with linux

also says DEFAULT CATCH!, code=300 at %SRRO: 0020b6e0 %SRR1: 00083030 ???? what does this mean