Let me get this straight. You have issues with FF5, not playing correctly stuff at aol.com?
Have you heard of IE Tab Plus which fakes IE with certain sites? v.2.3.x is compatible with FF5, and my FF5 portable had aol.com as home page, but, playing directly the way you described did not work, and neither 3.1.18 did. I don't have Google Chrome, which I reported gave me all sort of problems, but I tested the site with IE8.
IE8 burped as well as it could, but worked, so, I tried, again, FF3.1.18 which had IE Tab Plus, and it worked as poorly as IE8. Then, I went to FF5, and I install IE Tab Plus, and, sure enough it burped along beautifully.
I believe that Google Chrome is smart enough to sense sites like aol.com, so it should work for you. But, as far as Firefox is concerned it is another case of a microsoft-centric site, so it needs the addon.
By the way, aol.com is not this bad, all the times, but it has happened to me, in the past. Hardly a reason to dump Firefox, especially if I can't get Google Chrome to reinstall.
UserAgent: Mozilla/5.0 (Windows NT 5.1; rv:5.0) Gecko/20100101 Firefox/5.0