The url is the testcase from bug 371919. If I quickly click on the "Reload" button (in the testcase) a couple of times (like 10 times), the window disappears or becomes transparent (which reminds me of bug 391043. Btw, the testcase has hidechrome=true on the window element). There seems some resemblance of bug 322074 here when the window totally disappears for me. Unfortunately, it is very difficult to get a regression range, because I can't seem to get the bug reproduced very consistently in older builds. I'm marking this security sensitive for now, because disappearing windows or transparent windows shouldn't be possible with normal web content.

CTho and I have seen this with a xul popup testcase he wrote.

(In reply to comment #1) > CTho and I have seen this with a xul popup testcase he wrote. That's bug 378532.

should have been fixed by bug 322074. Martijn, do you agree?

Yeah, seems fixed, using: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9b3pre) Gecko/2008011005 Minefield/3.0b3pre