Resizing part. won't work!

[a monkey]

I just bought a brand new eMac - 1.25 GHZ, ATI Radeon 9200 video 
card... real nice machine. As soon as I got it, I thought, "I can't 
wait to install Yellow Dog on this baby!". Well, I did the usual - got 
out my Gentoo LiveCD, got to the patched version of parted, and typed 
"resize 3 128.031 bla". On my old Mac, it worked fine. But I got an 
error saying that the mount point could not be found, or it was 
unavailable, or something similar. Very strange. Can anybody tell me 
how to resize my HFS partition, and why I can't resize it the usual 
way?

Thanks,
the monker