Seems we're talking about the same thing. My MBP, although a bit newer than yours, has the same X1600 card as your, and a lot of iMacs (named in the other thread) and MacPros also have these problematic cards. It seems to affect a lot of ATI cards of several models, not just a few samples. But the issues started with Leopard (OSX 10.5), and did not happen with Tiger, so it might just as well be a software/driver issue, that hasn't been fixed until now.
If our problems continue, it would be good to know what info you have about the "known problem". Is that your designation, or is it Apple's, and did you get any documentation from them confirming this?
If somebody else has this problem under 10.5.7, please post!
AC4.1-AC26SWE; MacOS13.5.1; MP5,1+MBP16,1