D’oh! IE wmode bug…

If you are using IE - like I do most of the time - you may notice that occassionally the spinning cube in the header starts chugging horribly (and I mean horribly) when other SWFs are running on screen as well. (Edited: I ended up removing the SWF from the header - it was just causing too many headaches.)
I spent quite a bit of time trying to figure out what's causing this, and I was just about ready to climb into a nearby bell-tower and start picking off people when I finally found an explanation.

The cube SWF is running with its wmode set to "opaque" (instead of the default "window") to prevent it from rendering on top of other display-elements (e.g. the gallery pictures), and it turns out that this is triggering a buggy behavior in IE.

There's a great demonstration of the phenomenon right here:
http://justin.everett-church.com/wmode/

Ouch. What a bummer.