Thanks for the clarification! It sounds like you mean the left hand sidebar. You may want to try using a different browser to load the page to see if that is an issue isolated to your particular browser/add-on combination. Sometimes when members have extensions installed, one of them (or a certain combination of them), will cause unexpected issues with site performance. If you try a different browser just to see how that works, that can give us some information about what is causing the problem for you.
Another thing you can do is try disabling your extensions/add-ons in Firefox temporarily to see if that makes any difference. If you do that and DO see a difference, you can add them back in one at a time to see if you can isolate the particular extension that might be causing the problem.