First off, kshane, UNcheck any of those pesky auto update boxes, using this path: tools/options/advanced/update (tab). I have *nothing* checked on that screen. By doing it this way, YOU are in control of the auto update feature not only for FF itself, but also any themes & extensions. Keep in mind that when you install an older version, you'll have to go to that Update tab & uncheck everything as these boxes may come pre-checked. Not positive about this, tho, but it's better to be safe than sorry.......
I Googled 'older FF versions' and came up with this site, which has every version of Firefox there ever was:
http://www.oldapps.com/firefox.htm
This is just a suggestion, but I would recommend you make a sub-folder within Firefox for keeping these setup exe's. If you decide to uninstall what you already have, tho, take your newly downloaded setup exe & place it where it won't get uninstalled with the rest of FF. Ask me how I know this happens!
(and me on pokey dialup)
I keep all my old setup exes in a folder on another partition, so they're readily accessible whenever I need them.
When I went back to version 1.5.0.4, all that I imported in to my new profile were bookmarks.html. I started from scratch with everything else.
Seeing as how you aren't sure what is causing this inability to reach & cruise at Amazon, I would strongly recommend that you just import bookmarks and then go back & install your extensions & themes one by one.
Keep in mind that some of your extensions probably have been updated to the most recent FF version and may not work correctly with an older version. I found this not to be a problem. What I'd do is go to the extension author's website & get the extension for my version.
Hope this helps you, kshane, and once you install your older version, you'll be able to access Amazon just the way you used to.