Snapshots - can't take a snapshot with running VM

[Julian Robbins <julian.robbins@xxxxxxxxx>]

Hi

I'm quite new to KVM/libvirt0 so hope you can help

I'm using Ubuntu Lucid 10.04 and libvirt0 0.8.1

When I try a :-

snapshot create vm_name

I get an error, ie 'error -5 while writing'

Googling doesnt bring anything up. Taking snapshots of a vm when it isnt 
running works fine.

Can I really only create snapshots of a vm when it isnt running ?

--
Kind regards

Julian