Click on something to download. Anything at all (preferably something which will take longish). Save dialoge pops up. You can't click back to open browser windows. The Save window stays on top, with all others shaded. Expected: should be able to click back to other windows.
Resummarizing and upgrading to major. -> XP Apps: GUI Features
From discussion on #mozillazine, it sounds like this is specific to Mac OS X. Really -> XP Apps: GUI Features
Didn't see this one before. Appears to be a duplicate of bug 88709, though I like the severity of this one better. :-)
*** This bug has been marked as a duplicate of 88709 ***