Comment 5 for bug 665512

I can confirm that this is a samba problem: Downgrading to samba version 3.4.7 from lucid fixed the issue for me. I've uploaded a downgraded samba package to my PPA (but be warned, I bumped the epoch on those, so installing them will prevent future automatic updates):

https://launchpad.net/~thjaeger/+archive/ppa