resizing a partition involves resizing two things.
First you need to resize the filesystem and then the volume (the actual partition). In case of growing a partition use the reverse order
usually you use a filesystem specific tool to do the resize (like resize_reiserfs) and fdisk/cfdisk/parted to resize the partition. You should be very carefull not to move the startpoint of the partition, because if you do, the data on the reiserfs partition is no longer accessible.
My advice is to grab a livecd with gparted on it and use that to resize your partition (and possible fix the damage you might already have inflicted on this partition)
I've heard good rumours about
this livecd.
good luck
