ok i am new to fire fox but try these
in options
- general - try using ur system fonts and colors
- if possible DISABLE flash where ever possible
- privacy - increase the amount of cache to a LOT
- web features - disable images , just give it a try , since forum is mainly based on textual (sounds so much like .....

) content see if it speeds things up
- try fiddling with the java and javascript options
- no skins , minimal toolbars
- several options to open in new windows , change them to open in new tab .
- if u got scroll mouse , press scroll for open in new tab
- finally reinstall to the new version
risky
- open a single blank windows and press ctrl+t for like 20 tabs to open . if it opens file , prob must be with the site
- try increasing priority of firefox in task manager
"Since Light Traver faster than Sound thats why Many People Look Smart untill you hear them Speak"
- try removing sounds associated with apps if any
Switch to opera : u can even allocate amount of ram used by opera there