I feel like I should re-state my current issue for clarity, as my mental faculties aren't quite at their fullest in the wee hours.
So normally (read: before 39f) I run the game windowed and, of course, at the default size. With FPS set at 100 and GFPS at 50/60/100/whatever I can run the game perfectly smoothly until rather late-game (I play only Dwarf mode, only mods I've used are reveal and the embark-screen reveal thinger). World gen used to take a little bit before 39, but up to 39e it was going markedly faster (I'm sure stopping earlier didn't hurt).
Now then, with the release of 39f I've been unable to launch the game normally. It draws the initial window and vista immediately gives an error and closes the program. It does this whether fullscreen or windowed, normal dimensions or not. The error is in atioglxx.dll. I renamed the file to atioglxx.old to see if it work then, and it does.
However, when I run it this way things are very slow. Even with a default config I get a max FPS of about 30, and that's at title screen or after a fresh embark and paused. I unpause and it lowers to the lower twenties. It seems that it's constantly giving one core a max load at all times, which was not formerly the case.
Now, I interpret this as having manually killed gfx acceleration by renaming the file. Gripes about multi-core cpu support aside, are there any known courses of action to improve performance here, to restore acceleration support (I've done a full uninstall/wipe of ATI software & reinstall already), or to do something on my part for more troubleshooting/debugging?
As stated earlier, I'm running a 4870 with Catalyst 8.7 (non-beta/hotfix) w/CCC.