Another... Firefox problem

I've checked the other threads for my problem, or similarities to my problem, but haven't found any thus far.

Certain webpages do not load, or load horrifically slow, on my 7 box using firefox. I have the exact same setup on my laptop, and have not been able to duplicate the problem.

Certain web pages do not load, load very slow, or do not load updates. It's quite bizarre. Say I post an update on twitter. I refresh the page, and my update isn't there. If I refresh on another computer, it is there. I hit refresh again on my first computer, and it's there, I refresh again, and it's gone. Same with facebook and comments. gmail I create a message, add recipients, subject, and body, and click send. Then at the top it will say "Still working..." for an infinite amount of time. Clicking on certain links yield no problems.

I haven't been able to determine the cause of the problem. The only add-on I have is flash blocker. All these sites work fine on other computers. I tried disabling IPv6 connectivity.

(Incomplete) List of sites that have problems:
myspace.com
facebook.com
twitter.com
gmail.com

It seems to be anything with CRUD style programming. Simple websites, such as craigslist, youtube, and just about anything regular, have zero problems.

Any help would be greatly appriciated

These things did not solve the problem. It seems to be a programming incompatibility of some sort, but it didn't happen at first, only in the last few days, though nothing has changed. IE works fine and is fast with all of these pages.

try uninstalling that add-on.

I've already tried disabling/removing the add-on. the add-on on another machine works fine with no problems, in fact, i have it on every machine. I have the latest version of firefox. i have everything updated. I'm looking for known software incompatibilities. Thanks.