See this thread on Stream's forum I'll try it myself as I have the same issue with HD 6990:

http://forums.steampowered.com/forums/showthread.php?t=1911994

the problem with light bleeding happens to everyone with crossfire and cannot be fixed until new drivers or CAP are released

the problem with light bleeding happens to people with one card if they installed CAP3.

If i understand correctly the steam topic says uninstalling CAPs + ATI drivers and then installing them again fixes the light bleeding using one card but if using crossfire this is not fixed.

A 6990 is a dual gpu so i guess the solution for uninstalling and reinstalling won't fix the problem.

For those people getting the light bleeding in crossfire mode, download the latest version of RadeonPro, create a profile for Witcher2.exe and choose the Dirt2 crossfire in the tweak tab.
See the attached the picture for help.
That solved the problem for me, and kept the framerate high.
Hopefully the new CAP will fix the problem properly.

not for me, as i stated before it solves the problem but the fps are much much worser. Like 20 fps less in the prologue outside the tent (37 fps more or less with dirt2 profile vs 55-60 with witcher2 profile)

dirt2 profile is good for the cynematic scenes but not for ingame.

@CatalystCreator
Andrew D
Witcher 2 update - trying to work with the game developer to resolve the light source issue; fix in driver will really hurt the perf gains

@CatalystCreator
Andrew D
Mouse lag issue will be fixed in Catalyst 11.6 release (aiming for June 15th release)

pf... this seems pretty bad. Hope the issue is resolved soon but i don't like them saying they cannot fix it without loosing performance

Already gave up on ATi on this, ordered an MSI 570GTX Frozr III. Too many issues with ATI recently (Crysis 2, Witcher 2, Blink) and also my 2-Asus 4850's in CF keep overheating.

Shame as I would have liked to support them but for me they have dropped the ball way too often like when the 11.5b hotfix did not support Vista (which I use).

then stop using vista. simple fix. :P

Keep in mind that even though ATI has been having xfire trouble, Nvidia only just fixed their SLI TW2 today, and furthermore Nvidia had single card problems that ATI did not have at launch.

Actually I am planning to NOT run CF or SLI anymore, just had too many issues and CF/SLI is quite expensive, having a good solid single card solution plus enough CPU power to back it up is the way I will go.

just as an fyi, I did borrow a friends 560Ti to test out against my 2-4850's, knowing that CF is not really working (disabled it), the 560Ti was just a lot better, maybe 50% better using fraps and some experimental testing. I know i could have gone with a 6870 or 6950, but a lot of people here report problems and performance issues with those as well (which the hotfix has not yet fixed also).

Well, considering how CDPR has been acting towards customers and fans I'd say we should get a fix for CF pretty soon, they've been nothing but helpful and seem to do their best to fix any bugs, I'm sure ATI and CDPR will get us a fix. They'd better at least, I've played the game with 1 of my 5850s the first time, but I really want a solid 60FPS the 2nd time around, so I'll be waiting an playing something else meanwhile.

hey guys, i have only one gpu, this fix would improve something for me, or its just for people using cressfire?
thks in advance for the answer

They said it could bring small improvements to single-GPU users as well.

Interesting, I'm using 11.5b, CAP3, RadeonPro [Dirt2 Profile, with Alternate Frame Rendering], crossfired 5770's. There is no light flare issues.

I find the frame rates fine, [e.g. 35 to mid 40's in Vergen] but there is some stuttering going on when Geralt runs around, less so with Patch 1.2 though. This is also with AA x 4 [via RadeonPro] and SSAO set to enabled, 1920 x 1080, High settings.

It'll get fixed eventually, some games apparently take longer than others. In the future, I'll likely revert to buying games that have matured / stable.