I'm not sure if recent EAP upgrades (4244 currently) or the updated beta of JDK 1.6 (b85 on WinXP) are causing this, but I recently started getting the attached series of exceptions when I close the last editor tab. After the exception, it's not possible to open a file until IDEA is restarted. I usually work around the bug by always leaving at least 1 tab open.
Granted, I know that I shouldn't be running IDEA under 1.6, but it "feels" a whole lot faster (double-buffering -- I know it's an illusion, but it's a very nice illusion). Plus, this is the first reproducible problem that I've had using 1.6. I suspect that it's a JDK bug, but on the off chance that it's not, I thought I'd post it here.
Attachment not added (general error): "idea.log.gz"