I can't find the definitive answer.
I saw somewhere ubuntu9 is not supported, but I can't find the link
EDIT:
@LukeR.
Actually I performed the steps described the link you posted which are pretty much the normal way. The problem I had ( and now reading the link the poster did have too ) was installing the parallels tools.
From your link step 25:
...I’ll update this tutorial with the steps required to install Parallels Tools in Ubuntu 9.04 once Parallels updates (currently it doesn’t work).
Which lead me to this question. Parallels tools enable the use of full screen among other things ( afaik )
I'm running Parallels 4.0.3844 under 10.5.
Just finished installing 9.04. No problems at all.
On the Parallels website it doesn't give specific version numbers, only 'Ubuntu' under supported 32bit guests.
http://www.parallels.com/products/desktop/sr/
It would appear from a quick search that people have been successful in installing it though
http://www.simplehelp.net/2009/05/13/how-to-install-ubuntu-904-jaunty-jackalope-in-parallels-desktop-for-os-x/
Ubuntu shouldn't differ that much in between versions to warrant any special tweaking to the VM host software.
If they say Ubuntu is supported, then the latest version should work, regardless of what version they tested to say it was "supported".
I haven't had any problems with Ubuntu in VMWare or VirtualBox, so I would think that parallels would be the same.
Not quite an answer but related: VirtualBox supports Ubuntu fairly well. I run VirtualBox on my Mac to use windows Vista, but use VirtualBox on my windows computer to Run Ubuntu.
If you are having trouble getting Ubuntu to run on Parallels, try VirtualBox. It won't hurt.
Well, I finally got the answer.
No official support for 9.04 :(
I've tried this and I can't install parallels tools.
I've tried VirtualBox, as suggested by Frank. It doesn't quite feel like Parallels :)
I'll try version 8.
Has anyone installed triple boot camp? OSX+Windows+Linux?
:P