Oblivion and Crossfire

i don't actually have the game but its probably best to wait till the new drivers come out. that patch is just a stopgap till the main thing. maybe try forcing the AA and AF settings through the CCC. check the catalyst A.I settings as well. tbh even at that res a system like that should be fine.

blame the makers for shafting ATI users so as to keep nvidia happy.

This is indeed puzzling; those were about to be the VERY settings I was going to recommend for your sort of setup. Really, hardware-wise, you can't get much at all better than what you have.

Clearly, there's something wrong. A pair of X1900XTs, in CrossFire, even in "Scisors" mode, (I think Oblivion defaults to "SuperTiling," doesn't it?) should have no problem at that resolution, even with x6 AA.

I'm reminded of some problems I've encountered in Catalyst (5.x versions, though) with conflicting AA settings in-game and in the control centre/panel. I'd make sure to fiddle with these to find the source of the problem. Perhaps, once you find the source, see what you can do to have AA without the problem. I might guess something like editing the
Oblivion.INI file (look for the line, "multisample type=0" ) to change it to enable AA right in there, as well as in the CCC, and see what that does. (of course, after ANY graphical settings changes in the INI file, do NOT enter the graphics settings in-game, else you wind up dumping all your changes)

That's an incendiary statement if there ever was one. Far from the truth as well; if Bethesda was intent on making the game a "TWIMTBP" title, aside from having the logo, they might've actually strived to make framerates on high-end GeForce 6 cards be BETTER than those of mid-range Radeon X cards. Likewise, it's been noted that a GeForce 5900 ultra, in Oblivion, is a good competitor to the Radeon 9600pro.