i have ubuntu 10.10 running on an ibm thinkpad T43p.
when i try to hibernate, this fails very often. sometimes i just get back a login screen (as if i had locked the screen) after about a minute of harddisk activity, sometimes the screen goes black but discs and fans keep running.
and - yes - sometimes it just works as it should.
i have a huge amount of free swap space. that can not be the issue.