lvm2 snapshot

I have Debian 3.1 with 2.6.13 kernel. I made LVM2 logical volume, made fs,
mounted it - that's all right with it.
But I failed to make a snapshot
lvcreate -s -L500M -nsnap1 /dev/vg00/news just outputs
as if it was initiated like this lvcreate -h
and nothing else, no error messages.
/dev/vg00/news is my previously created volume.
What I am doing wrong? I just didn't expect to get a problem in such a
place.