Tabs won't die?

I'm seeing some odd behavior with 4.0; I have multiple files up for editing, and none of the "close" functionality works on some tabs. Close, close all but this, etc. Some tabs (and their files) just stick and I can't be rid of them.

When this happens, clicking on another tab goes to the right file, but the tab isn't highlighted. it's like the tab bar is "frozen".

Any thoughts?