FireFox problem...................

Go thru the settings and be sure FF is not set to check for updates at startup; if you have a lot of addons, that could take some time.
I use the same version of FF and Comcast is also my provider. I'm not getting what you are. I also have two home pages set to load at startup. I have my cache set to 50 MB and 0 days history. I also have FF wipe everything when I shut it down. ymmv

 

1. Click on Tools then Options and you'll get a popup screen - that's where all your settings are located.
2. First tab, Main: I have checked/ticked the last item "Always check to see if Firefox is the default browser on startup". I fire up IE and Opera to check how sites load but I do want FF to be my default so that's why it is checked.
3. Last tab, Advanced, has several tabs within it: click on the third one, Update (the default has everything checking for updates and that can slow you down). I always uncheck Automatically check for updates to Firefox, Installed Addons and Search Engines. You may notice a speedup. Before you close the window, click on Okay at the bottom or the changes will not be saved.
4. the 5th tab is privacy: that's where you decide if you want FF to keep a history of the sites you browsed and if so, how many days. The default is 9 or 10. You can make it longer, shorter or even uncheck everything so if the browser is closed, all the sites are gone if you did not bookmark them.
The very last item on that page has the heading Private Data
I have checked/ticked "always clear my private data" then you can click on the settings button and decide what exactly you would like FF to wipe when it closes. If you only want the browser cache cleared, the only check/tick that item. If you aren't sure, leave them all unchecked/unticked and nothing will be cleared.

Look over the other sections and if you have questions on any of the settings, feel free to ask.