I am really stuck!

I followed some great advice while researching how to dual boot my mac powerbook G4 with OS X and Ubuntu.

During the install I have so far achieved the following:

The partition to shrink is no 5:

Number Start End Size File System Name
1 1kb 32kb 32kb Apple
2 33kb 65kb 33kb Macintosh
3 66kb 98kb 33kb Macintosh
4 98kb 360kb 262kb Patch Partition
5 360kb 60GB 60GB hfs+ MacOS

and the command I entered in parted was:
resize 5 360kb 45MB

Then I got this error:
Error: Trying to register an extent starting block at 0xAF0429, but another one already exists at this position. You should check the file system!
Error: Could not cache the file system in memory.
Error: Data relocation has failed.
Error: Resizing the HFS+ volume has failed.

Any help would be very much appreciated. Thanks.