Which effects does this happen with? Does it only happen with some effects? Are you running the full version of After Effects or the trial version? Have you updated to the most recent version (9.0.2)? What operating system are you running?
Most critically: What processor? Effects not being able to load points to an incompatible processor that lacks the necessary SSE extensions or some other feature. Often this also points to missing system extensions and DLLs that are responsible for some of that. Also provide info about your OpenGL settings and hardware. Effects may also throw errors if you are attempting to run them with acceleration, but your graphics hardware is unsuitable.
never mind. i un/reinstalled and it works.