Yeah I have the same problem. I'm using SuSe and the model-specific drivers just don't want to work, even the manufacture supplied drivers I downloaded. I have tried to get my installation working and the only thing that gets it running is good 'ol VESA.
According msinfo32, I have an ATI Radeon X600 PRO (0x5B62) with 128mb of RAM (but I disgress, I think there is 256 megs split between the two adapters (Primary and Secondary) that windows installs, urgh...). Anyways, on WinDoze XP the manufacturer's drivers work like a charm, DirectX and all. Sax2 says it's an ATI Radeon X600 (RV370) 5B62, so it appears to have the right driver.
Other system specs of interest is P4 3.2 Ghz, a SB Audigy 2 ZS (with 5.1 surround sound speakers plugged in), and an ASUS m'board.
o After running xf86config in failsafe and selecting "Ati Radeon (generic)", I can type startx and I get as far as the hashy background pattern, but that's it. The cursor updates for about 5-10 secs and then it freezes. (by this stage Ctrl-Alt-Bkspc doesn't work, and my CPU fan is about to take off since the CPU is hung.)
o I can use Sax2 to select the FireGL drivers from ATI, but they crash during testing after displaying a dialog box (no text appears on the dialog box, for some reason) with a bevel across the middle. Again the three-finger-salute doesn't work and it's time to hit the reset button.