I know this thread is really old, but I just tried reducing a logical volume with the command:
lvreduce /dev/VolGroup00/LogVol02 --size <can't remember what size I reduced to>
and now when I try to boot, I get many errors and then get dropped to a shell. I get messages saying that the I have a bad super block on LogVol00 and that the partition table is corrupt.
I'm really not sure what to do since I don't have too much experience with logical volumes. I can boot and login with the rescue CD or login as root after I get these errors, so all is not lost, but I do have a lot of data on these volumes that I absolutely need to recover so you can understand that any help would be much appreciated.