1. Make sure that you have updated CS6 to the latest build.
2. If that does not solve the problem we need to know something about your system specs, your operating system and your composition. Just about anything from inadequate ram to the type of footage you are using could be causing a problem.
Without knowing anything about your system, your footage, your comp, your effect settings and so on nobody can say anything.
Well I only have version CS3, however I got the same error while trying to open Knoll Light Factory plug-in. I tried several times and it never worked. I searched and found a couple of 'fixes' but they didn't work (for me).
What did fix my problem, I looked inside the After Effects directory, specifically at C:\Adobe\Adobe After Effects CS3\Support Files\(PCI)\Setup\... - inside this directory is the file 'Setup.exe'. This setup file is the Adobe After Effects Third Party Content Installer. I ran this setup file, after it finished doing it's thing, and without rebooting, I opened AE, loaded a project and went to Effects and the KLF plug-in. I chose it and it opened perfectly without any glitches or errors. I'm not saying it will work for everyone but it did for me. Not sure if there is any difference in versions as well, like I said, I'm using CS3. I have since rebooted a couple of times and no problems with AE or the plug-ins (fingers-crossed).