The current version 3.3.1 is making Firefox 6.0.3-64 on Windows 7 very slow (page loading) and nearly unusable (response time). So I started Firefox with disabled Extensions and it worked perfectly well - very fast and stable. By trail and error, I enabled Extension by Extension. So my final conclusion was to disable the Adblock Plus Extension :-)
PS: Was using the Extension for years without any problems!

Сито с рваным дном. В браузере Мозилла почти не работает

Good

OUTSTANDING!