I don't know what really happened with the combination of FF30 and Firebug2.0 but it stops me from using it.I don't have the time, nor I feel like digging into bugs to properly report them, since I've lost enough productive time already fighting with it. I reset all settings but problems seem to be persistent.
I have the following addons enabled: Adblock plus 2.6.3, Colorzilla 2.8, Disconnect 3.14.0, Faviconizetab 1.0.6, Firebug 2.0, Firequery 1.4.1, Greek spelling dictionary 0.8.5, gTranslate 0.9, ImageZoom 0.6.3, Multilinks 3.0.0.19, TamperData 11.0.1, WebDeveloper 1.2.5.
If there is something I need to do, please let me know. I like this addon and want to continue using it, but not under these circumstances. Thanks guys for the effort so far.