Hi Rury,
You can start by trashing FC preferences and this might helps, but when FC slows down or misbehave is much more possible that the problem is out of of FC than in the very application. If your system doesn't run well no application can run well, if your HDs slow down every application that needs fast read/reading will slow down.
System a HD maintenance is important to make FC work fast.
Start by repairing Disk Permissions. If that doesn't helps I suggest you something like DiskWarrior or TechTools. make sure that your HDs are not too full. You can also check your HDs speed.
rafael
http://www.nagavideo.com