Try making a new profile Profile Manager - Create, remove or switch Firefox profiles

If you had any important data in your profile try to recover it by following http://support.mozilla.com/en-US/kb/Recovering+important+data+from+an+old+profile

Unfortunately this was done in a mass deployment to literally hundreds of machines. Many of these folks are not technical. The best solution at this point to is to roll back to FF 3.6.16 or tell them to switch to Safari or Chrome. I'm leaning towards the latter.

gmail in standard view delays to much in FF4 ,then i switch to basic HTML it loads faster and then again to standard view and works fine why?, in chrome or IE9 works OK.

Had this problem too. Works after deleting the profile folder located in: (Drive):\Users\(Username)\AppData\Local\Mozilla\Firefox\Profiles (youll still have your bookmarks etc.) Still, doesnt work out of the box if upgrading for some reason for gmail and certain parts of js heavy sites...

Deleting the profile folder works once, but loading the mail again happens the same, I'm using HTML, then switch to standard is faster

I found that opening gmail directly in google , opens immediately, but in a new tab (as i use to do) it delays to open several minutes, perhaps this will help meanwhile FF fixes it

I had the same problem too using FF4 with extremely slow Gmail load issues... I solved my issue by doing the following:

• Restart Firefox with Add-ons disabled: Click Here for Firefox Support Article (click on Firefox menu > Help > Restart with Add-ons Disabled)
• login to gmail or your site(s) that are causing you trouble to see if the issue is still occurring with all of your add-ons disabled. Most likely you will notice that everything appears to load correctly, hence it's one of your add-ons that are causing the issue.
• restart Firefox so that all of your add-ons are enabled again
• if you notice that one of your add-ons are the culprit, disable them one by one and try to login to Gmail or one of the other sites that is failing to load. NOTE: If you have a lot of add-ons, this will take some time since a restart of Firefox is required for the add-on to technically be disabled. (remember to do this one at a time so you can see which one is the culprit by process of elimination)
• Once you find the culprit(s) add-on(s) that are giving you the issue, disable the problem add-on and enable all the other ones and restart Firefox. Then you should see the site that was causing you trouble will load normally now.

- I found the add-on that was causing my Gmail to 'get stuck' on loading the standard view was the "McAfee Site Advisor" add-on. I disabled McAfee Site Advisor and all is well now.

I hope this helps anyone who is frustrated with the same issue that I had.

Nate

Solution found in:

http://www.geckoandfly.com/9002/solution-firefox-4-slow-hardware-acceleration/

Hope it helps

I had the same problem for weeks, started using Chrome instead, kept going back to check, I did all the suggestions of clearing cache, deleting cookies, uninstalling Firefox 4 and reinstalling it, error check, Malware check, virus scan, etc., etc., nothing worked, MAKING A NEW PROFILE WORKED. See link at first reply for directions.

I went to task manager in Vista, found there was a firefox process running (although all browser windows were closed), killed the process, and all is good now. Easy fix.