Could be a preferences problem, which can happen if you reconfigure your monitors or previewing hardware. Try removing the Color Finesse prefs file which is "~/Library/Preferences/Color Finesse 2 UI.plist". Just trash it and try Color Finesse again.
If that doesn't help, let me know how far into the launch of the UI it gets. You should see a yellow splash screen, with some progress information in the lower right corner. How far it gets through that can help isolate the problem.
Also, which version of OS X are you running?
Or, re-reading more carefully, are you getting a crash of After Effects itself when applying Color Finesse to a layer?
the crash occurs when I click to view the "Full Interface" of ColorFinesse. I'll try the preference dump and see if that helps,
and I'm running OSX 10.5.8
A common cause for woe in AE 9 is the nature of the footage. What's the media container and the codec of your video?
Another thing to try: turn off multiprocessing and turn off Open GL acceleration.
The media is on my Hardrive and there's no codec, just a png sequence rendered from 3D Studio Max.
I have Open GL turned off already (it never seemed to work in AE anyway).
I've been researching older bug reports for Color Finesse 2.1 and can't find anything that applies to your situation. Version 2.1.12 has fixes for some bugs that give similar symptoms, but you're already running that.
One thing to check is to make sure that you don't have a mix of versions of Color Finesse. Make sure that when you run the 2.1.12 installer that you manually point the installer to the After Effects Plug-ins folder. It won't find it automatically, and with CF 2.1 that can give you a mismatch between the plug-in and the UI app. That shouldn't crash, but it also won't work right.
Also, if you can send us the crash reports we can analyze those and see what we can figure out. Send them to support "at" synthetic-ap "dot" com.
I've already reinstalled the latest version of CF 2.1.12 and did the manual-install-into-the-right-folder thing you suggested as well.
I've sent the crash report to the email address you gave.
Thanks for your help.