Could a broken HTTP proxy be in your way? You can look at your HTTP traffic in Chrome by hitting F12 and clicking on the ‘Network’ tab, or in Firefox by installing the HttpFox addon. You can click around on the requests/responses and see if you’re getting any strange error responses.
Also, have you tried ctrl-shift-r to force reload in both browsers? Some broken resource might be cached.
Excessive returns will possibly get you banned from Amazon for life, with no warning, as many have discovered.