Cannot login with Firefox 4.0.1: Page Not Found

Question

I observe the same behaviour with Firefox 4.0.1 as described in Cannot login with Opera: Page Not Found. I use the same procedure and observe the same outcome. It neither works with Firefox started in SafeMode with all add-ons deactivated.

Internet Explorer 9 is OK.

Answer 1

You're exhibiting this error. The first person I've actually got "on the line" who has encountered it.

I'm going to go out on a limb and say this is your ISP doing something very... internet-breaky. IE 9 working (I'm guessing intermittently) is odd, but I can imagine bogus caching rules that would allow it.

Anyway, from your IP address I've logged the following:

Cache-Control: no-cache 
Accept: text/html, application/xml;q=0.9, application/xhtml+xml, image/png, image/webp, image/jpeg, image/gif, image/x-xbitmap, */*;q=0.1 
Accept-Encoding: gzip, deflate 
Accept-Language: de-DE,de;q=0.9,en;q=0.8 
Cookie: canary=1; anon=[REDACTED]
Host: openid.stackexchange.com 
User-Agent: Opera/9.80 (Windows NT 6.1; U; de) Presto/2.8.131 Version/11.11 
[IP REDACTED]

And

Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8 
Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7 
Accept-Encoding: gzip, deflate 
Accept-Language: de-de,de;q=0.8,en;q=0.6,en-us;q=0.4,es;q=0.2 
Host: openid.stackexchange.com 
User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:2.0.1) Gecko/20100101 Firefox/4.0.1 
[IP REDACTED]
DNT: 1

Both as GETs to /affiliate/form/login/submit, which expects POSTs. This is very very wrong. Could you do a traffic capture* to see if this is your browser (for some crazy reason) submitting GETs instead of POSTs, or whether it's a proxy/ISP doing the conversion down the line?

Confirmed: These requests are arriving at our network as GETs, but leaving the browser as POST. Tricky...

Also note, that FireFox's "Do Not Track" behavior (what with not accepting cookies, and that DNT header) will break this as well. The GET instead of POST is just the first thing that explodes.

_{*Firebug (or the Opera equivalent, if there is one) would be best, HTTPS makes proper capture a bit of a pain.}

Answer 2

When we see this, it is usually because the browser is misconfigured or has rogue plug-ins.

Try it in Firefox Safe Mode -- hold down shift while starting the browser:

http://blog.mozilla.com/rstrong/2011/01/21/windows-safe-mode-and-shortcut-changes-for-firefox-4-0-beta-10/