hello, in which context are those pop-ups showing up - on every page? this might be sign of malware active on your pc. please remove all toolbars or other potentially unwanted software or software that you can't account for in firefox/tools > addons > extensions and in the windows control panel. also do a full scan of your system with your security software.

Troubleshoot Firefox issues caused by malware

No. Not every page. I have run a malware scan and nothing came up. The popups are advertisements and they open in new windows...not just a new tab (like most allowed popups do).

ok, then this was possibly a false alarm :-)

you can also use an addon like adblock plus & a filterlist to get rid of more pop-ups and adverts.

Ok. Thanks. I'll give it a try.

I am having the same problem also although I use add block plus. I have flash and other adds on pages where I did not have before. I also use chrome and IE but do not have the problem with those browsers.