I brought up Process Viewer as Marcus suggested above and the results are very interesting.

Ours may indeed be a CPU problem, but NOT from LimeWire (at least not directly). Over the last ten minutes LimeWire has claimed between 20% - 40% or the CPU, my browser 5 - 25%, and Window Manager 30 - 70%!!!

Window Manager??

I've played around a bit running various applications together and singularly. If you see Window Manager at all, it's very briefly and at 5% CPU at most. Once LimeWire is loaded, Window Manager moves to the top of the CPU column and stays there.

Just now, I brought up a third large application (AppleWorks). Window Manager jumped up to 85%. It took nearly 5 minutes until I could exit AppleWorks and return to this post. Window Manager continued to sit at 82% for another minute or two, then returned to 31%.

I suspect we're seeing a LimeWire - OS X conflict. Maybe LimeWire defines its windows in a non-standard fashon.

Any ideas?