I implemented the fix (changed setnz to setz) as Arisu described and it appears to be working at Helgen's still.
Here is the file. It is version 1 with just the setnz to setz fix for Patches.replace.test_bit_30
I used 4shared to host it as someone suggested.
http://www.4shared.com/zip/y9_xxsOw/TESVAL_v1_with_fix.html?
Please let us know how if you find any bugs.
This fix (changing a single letter in the code as suggested by Asiru) while fixing the bugs it caused also seems to improve performance even more for me. Whiterun was a general overall improvement with the worst spot (on those steps overlooking the town up towards Dragonsreach) gaining me another 3-5 fps so I'm now at ~35 fps on those steps. Markarth is a tougher animal with its worst spot (right outside the door to the Jarl's place staring at the rock face below the Temple of Dibella entrance) at 20 fps (stock is 15 fps for that spot) BUT, and this is a big but, the bad spot is now smaller. Just moving the camera a tiny amount rockets FPS up by 10, move it more and it's in the 40's. Whatever is going on in Markarth is reduced significantly by this newest revision. Instead of entire directions being super low fps, it now seems to be small specific points. Overall Whiterun is in the high 40s to 50s for me and Markarth is now solidly in the 30's. Huge improvement, say ~35% overall in tough areas.
AMD Phenom 2 x6 @~2.6 ghz
AMD HD 6850 stock
6gb Ram
Win 7 64 bit
If anyone cares what my specs are. I'm also running tons of mods, they change every time I load the game.