System Freezing?

I have seen this on both a mid-2011 iMac i7 with 16 GB RAM and on a mid-2011 MacBook Pro 15 inch with 16 GB RAM. Everything just freezes. The cursor moves around the screen but nothing can be accessed by mouse or keyboard. My clock is set to show seconds and it is frozen. This has happened 3 times in one day on my MBP and a couple of times on my iMac. Kind of hard to figure out what is going on because there is no crash. This is happening while using FCP X. Have not seen it in other uses. This seems to be happening since the 10.0.6 update but I'm not sure if that is coincidence or not. Anyone else seeing this?

I've noticed that a few free plugins have some problems like this. I've even had some plugins that once or twice caused me to have to delete and reinstall FCPX. Have you noticed it happening while doing anything specific and repeatable? like browsing through effects plugins, or even fonts.

I had a couple of problem fonts but sorted that out a while ago. I haven't seen any common denominator as to when or why this is happening now. I'll keep working at it. Thanks