> With various versions of firefox under NetBSD and Linux, I frequently get
> an empty dialog or popup when I submit some form. This has been happening
> for a couple months.
> 
> Have a look at this small image:
> http://pilchuck.reedmedia.net/jeremy/ictyg34o/unnamed-firefox-popup.gif
> 
> Anyone know what this is? And how to fix this?

I believe it's something related to remembering passwords - and for
me, was exacerbated by running the linux binary of firefox. Did you
delete everything, including history.dat?