I have the same problem and it's very annoying.

As soon as I installed 3.6.8 it is slow as hell.

I did get some improvement by DISABLING "no script"

I don't know if this is the right solution

 i HAVE THE SAME PROBLEM @ THIS WAS SUPPOSE TO BE A F-A-S-T-E-R SITE !!!! I CAN'T SEE THAT HAPPENING YET PLUS THOSE POP UP'S THAT WON'T LET ME GO WHERE I WANT TO GO ALL I GET DONE IS CLICK ALLOW ABOUT 50 TIMES @ STILL GET NO WHERE..I'M ABOUT READY TO GO BACK TO DIAL UP..IT IS SLOW BUT AT LEAST I CAN GET WHERE I NEED TO GO @ NOT SPEND ALL DAY CLICKING ALLOW ALL DAY LONG..HOPE YOU ALL AREN'T HAVING THE SAME PROBLEMS!!!! IT GET TO BE VERY NERVE RACKING..i DON'T TELL ANYONE THAT THIS SITE IS A GOOD ONE, PLUS YOU CAN'T GET HELP WHEN YOU NEED IT

Disable "JAVA Quick Starter" in tools/add-ons/extensions.

I too had the same problem. Fx (3.6.x on Windows 7-x64 Home Premium) needed a long time to start, with a lot of hard disk activity. Solved it by cleaning up Java (version 6 update 21) with JavaRa.

Te be clear: Java functioned, and it still does, without any problem on my pc.

I have only this one version of Java installed.

I took the following steps:

1. First I made sure I had only 1 version running of the Java plugins/addons in Fx. I have Java Platform SE 6 u21 and the Java Deployment Toolkit, both version 6.0.210.7, and Java Console 6.0.21 installed.
2. I downloaded JavaRa from http://raproducts.org/wordpress/software
3. I then closed Fx and ran JavaRa
4. I chose the option: 'Remove Older Versions', even though I didnt have any older version of Java installed. It found and removed some older Java files and registry-entries anyway.
5. Then I used the option 'Additional Tasks' and checked 'Remove Useless JRE Files'.
6. After this I closed JavaRa and ran Fx again.

Problem solved, Fx booted up within a few (2-5) seconds instead of 20-30 seconds. I hope others can benefit from this. I suspect Java is often the cause of Fx starting very slowly.