FF x64 v.6.0 Not Responding

This problem has come up for the first time since I've had it (this installation is about a month old); switching between filters or simply cutting and pasting a group from one filter to another is causing FF to lock up for long periods of time. The Task Manager confirms the status as "Not Responding" and restarting the program, or the whole system, has not helped. There's plenty of free memory and CPU processing available, so it's not a system resource issue. FF is just choking on tasks that are normally instantaneous.

This might be two separate issues; the filters I'm trying are all "slow rendering" on one hand, and having issues with the clipboard on the other. Not sure how to tell.

Edit: Okay, I finally got into a filter for some poking and prodding; I seem to be experiencing a general, heavy lag. Never a problem before today, but I'm not doing anything different from the past few weeks.

Still having serious issues with lag. I'll search the forum a bit, but it seems like the closer I get to the effect I'm trying for, the more likely FF will lock up on the slightest change. It takes forever for FF to deal with something as simple as connecting two components, or just trying to delete one when I've hit some mysterious critical mass.