UPDATE: This bug is fixed in the After Effects CS5 (10.0.2) update.
We’ve gotten a few reports of crashes when applying the Directional Blur effect (and modifying its properties) in After Effects CS5 on a 12-core Mac.
First, we want to thank everyone who submitted a bug report. The detailed bug reports helped us to narrow down the issue relatively quickly.
It appears that there’s an issue that only arises when a very large number of threads is used by the Directional Blur effect, and that number of threads is only attainable on a computer with a very large number of processor cores (like a 12-core Mac with hyperthreading).
The workaround that has worked for us in testing is to remove the Mthread plug-in before starting After Effects (e.g., by dragging the plug-in to the desktop). The plug-in is in the following folder: Applications/Adobe After Effects CS5/Plug-ins/Extensions
Removing the Mthread plug-in disables multithreading, which prevents the effect from creating the overly large number of threads. Of course, this also means that you won’t get the significant performance improvement of multithreaded effects, so you probably don’t want to remove the Mthread plug-in unless you really need to get past the crash caused by the Directional Blur effect. You should put the Mthread plug-in back after you’ve gotten past the crashing issue with the Directional Blur effect.
If you have encountered a crash with the Directional Blur effect, please let us know whether this workaround works for you by responding on this thread. (Don’t respond in comments on this blog post. It’s much harder to have a conversation in comments on a blog post than on a forum thread.)
We are working on a much better fix now that addresses the issue with the effect plug-in directly.