resizing partition

[-::ubermann::-]

hi, i want to resize my mac partition, i have hfs journaled file system
i enter command sudo diskutil resizeVolume disk0s2 40G
but...it says:

Resizing encountered error The chosen size is not valid for the chosen filesystem (-9962) on disk disk0s2 macos

where do i see what size is correct, also i find it weird, when i partitioned from disk utility during installation i entered an arbitrary size..also i have another partition, formatted in reiser where i have suse installed, do i have to leave this as free space?

http://img138.imageshack.us/img138/9885/picture3rd0.jpg

[richard.mac]

if your using Leopard Disk Utility allows no destructive partitioning.