Recently I changed my nVidia GeForce FX5700 for an ATi 9600PRO. Downloaded Catalyst 9.11 (latest for that video card) and started the problems with LFS.

I can play any game I want (like GTR2, GTL and others) and someteimes the framerate slows down a bit but I can play for as long as I want.

When I play LFS sometimes the framerate goes down to 20-30fps, normally I play with 90fps, and sometimes the game stops responding. The Catalyst signs an alarm and closes LFS.

I'm going crazy and already miss 2 races because of this problem. I'm thinking about getting a new GeForce 7300GT, but I have to do something with this ATi.

Try to reinstall your drivers without Catalyst. So you basicly only install the drivers, not the catalyst control center.

Should I uninstall the Catalyst before?

1) uninstall all ATI-related software

2) reboot

3) install newest display-driver without ATI.Catalyst (driver only)

4) reboot

5) download and install ATI-TrayTools (ATT) http://downloads.guru3d.com/download.php?det=733

6) start ATT, define some game-profiles, have fun

Edit:
AtiTrayTools is a 100% replacement for the so called "catalyst control center".

For old Radeons like the 9600 , use Omega drivers, and all your problems gona be fixed

Or if you want , install the 5.5 CT for the 9600

My GeForce 5700 failed due to overheating, the fan was damaged, so I installed an extra fan for this video card.

So far I've done what VOID said and seems to be working fine. Gotta try it a little more.

And hopefully can get the GeForce 7300GT soon...

ATi 9600PRO has been excelent graphics cards, in nice old times when AMD was not present in ATI. But from AMD times there are many problems with ATI cards and drivers (cca from 2005-2006, from Radeon HD2000 series). And most worse are newest style Catalyst versions from 9.10. There are 2 solutions:
1. Install drivers only, but not whole Catalyst pack, as said VoiD.
or next better solution
2. Download and install older Catalyst version up to 9.8 (but NO newer), and intall it fully whole Catalyst pack.

Older Catalysts up to 9.8 (may be 9.9) are better as 9.10 and all newer! (I have tested most Catalyst versions from 2000 up to 10.1 with many ATI Radeon cards)

Sorry I forget,
as say Inouva, the ATI 9600Pro is older card, it may be, that you will need to install most older version of Catalyst (older as last good 9.8). Radeon9600Pro cards from the years 2002-2003-2004, that drivers optimalisation may be best on these years, and few years after it. If Catalyst 9.8 will not good, then try most older version.

@ Gachaves

Did you remove/uninstall all the nvidia drivers before installing the ATI software?

SD.

After a driver/cab cleaner and upgrade to 9600 pro, I had to install the full driver + CCC pack. Then reboot and delete the CCC and install ATI tray tools instead.

Long way round but only way I could get it to work

Yes I unistalled all nVidia related software before installing ATi.

I have to do the same: first install full driver+CCC, reboot, uninstall CCC, reboot, install ATT and now seems to be working.

I really miss nVidia...