I've just installed Ubuntu Feisty on VMWare Fusion and it works great. I got a licince for Parallels but, Parallels does NOT support Ubuntu out of the box! Get a fix please!
I have a Ubuntu 6.10 running perfect on Parallels. Feisty is still in beta, give the guys at Parallel a break when it comes to beta software, it is just released few days ago! Some folks get it working, check http://forum.parallels.com/showthread.php?t=10297&highlight=Feisty
I've installed ubuntu/kubuntu on parallels with no problems whatsoever? - the lack of Tools of Linux made me uninstall it pretty quickly though.
We're working on this topic. Be sure this will be available very soon. A lot of people here in the development also miss those linux tools...