Hi,
I am also using adblock plus and at times facing script hanging errors. But if i allow advertisement in this site, then sometimes loading of advertisement does not allow you to do anything. Adblock plus blocks DOM and so may be this behaviour. But if the advertisements load quickly , you could not any problem with any browser. But , loading of advertisement, for each of the tab changing actions, in the top as well as bottoms cause this freezing.
I use adblock to block this advertisement annoyance, but then if you go normal , then this problem of advertisement load hanging, particularly of object type of advertisement.
I also read about the safety of this add on on the net, but still there is no cure for this firefox freezing. If you reset firefox, you bound to loose all passwords for sites among other custom settings.