i think it mostly happen when u open a pop-up, so a workaround might be
goto about:config
and change the value of "privacy.popups.disable_from_plugins" to "3", default is "2"
how do i get to about:config? thanks
Background
To get around the default popup blocker, some sites use Flash or Java applets to open unrequested windows. This preference controls popups initiated by plugins.
Possible values and their effects
0
No restrictions on plugin initiated popups.
1
Limit the number of plugin initiated popups to value defined in dom.popup_maximum. (even with popup blocker disabled)
2
Block all plugin initiated popups. (whitelisted sites will still be able to open popups) (Default in Firefox 1.5 and above)
3
Block all plugin initiated popups, even those on whitelisted sites.
Caveats
Though rare, some plugin content produces legitimate (requested) popups. You will need to manually add such sites to your popup whitelist if this preference is 2.
I'm not so sure this is a pop-up issue, Clev....
Look at this:
http://ruk.ca/discuss/3917
Well, in any event, of all of these people, someone should be noticing an actual pop-up if pop-ups were causing this problem, shouldn't they?
There was one user in there that suggested Google Toolbar causes this... I've personally never used Google Toolbar. Sometimes, I have also noted, however, that if FF stops responding to the KB, changing focus to another app and back also occasionally resolves this.
Of late I've been using Safari, too, but I do remember this happening occasionally and not seeing an obvious solution.
The one other thing though, that occasionally is an issue, is migrating a profile from FF 1.5 to FF 2.0 -- I've had disastrous results with this. FF 2 only really began working stably for me when I deleted my Profile before installing it.