Firefox SloooooooooooW to start again after it updated

Hi all. Trying to get Norton to look into why, everytime Firefox updates it takes ages to load. If I disable Norton  antivirus auto-protect.  Then it starts up fine. So to me there seems to be a problem with Norton interacting with each new update of Firefox. Its getting to be such a pain in the arse, so much so I am thinking of dumping Norton when it runs out in 20 days. Shame as I`ve stuck by them since the days of windows 95.God knows how much money they have had off me in that time. Running Windows 7, 64. Norton product is Norton Internet Security version 21.7.0.11 all live updates run till no more show. Trusteer end point Emerald Build 1404.84 . Disabling Trusteer makes no difference. Only turning off antivirus auto-protect. So in order to use Firefox I am having to turn off Auto-protect. Start Firefox and then turn on Antivirus again. Bloody stupid. GET IT SORTED NORTON