FAQ/x64 limits

From VFXPedia

Fusion x64 offers the capability for users to take full advantage of their 64 bit systems and utilize all the system resources. The limitations currently are that not all plugins and API's are 64 bit compatible at this time. Quicktime and AEPlugins are not supported in 64 bit, and the majority of Fusion's own plugins need to be recompiled for 64 bit.

If you need AEPlugins, Quicktime, or a Fusion plugin that has not been recompiled at this time, you are able to run the 32 bit version of Fusion under the 64 bit OS.