jdk: once again thanks for all the help you have given me.

Success, I managed to install the ATI Radeon 9550 driver, however it was on Ubuntu 8.04 Hardy. After a day of going through page after page in google I discovered one recurring theme: Intrepid. I have now removed Intrepid from my system and am back to using Hardy and the driver installed perfectly first go. It appears that this is another bug that Ubuntu have not fixed yet. Until I see a fix on a few of the many posts that are (remarkably) similar to mine then I will stick with Hardy for the time being.

There you go! Radeon 9550 RULES! Hardy, YAY! Intrepid, BOO!
Anyway, I'm happy you finally sorted it out.
Cheers,
jdk

I've been following along this post with the exact same problems as kmacphail. Couldn't get the drivers working under 8.1. I did just upgrade to 9.04 however and now the video works great. No choppy movies or flash at all.

I intend to attempt an ati driver install (as i'm assuming it's better than the default ubuntu driver) but I'm nervous that I'll screw it up, and not be able to revert. Any tips on 'backing up' my current config so I can at least get it back to this state if the ati driver doesn't work?

Dear Tizzod,
It is really not a good idea to start a new thread inside an old one. This is called "hijacking" and it's frowned upon (with good reason). Your question is related to the original thread but that thread is now so old that you will probably get very few answers to your questions. I am only reading it because I responded to the earlier thread and I get notified by email every time someone adds something.

I'd suggest you repost your question WITH A VERY DESCRIPTIVE TITLE like "Installing ati drivers in ubuntu 9.04" and put it in the Linux Distributions/Ubuntu forum and you'll get all the expert help you need.
Cheers,
jdk

I wanted to comment on the fact that upgrading to 9.04 fixed the main issues of what this thread was dealing with. My question at the end was actually more of an afterthought when I was posting.