I have been having terrible trouble logging-in on one social network site for the past week, getting only error 500, using Google Chrome or Chromium but Firefox 10 & 11, Iceweasel 13, and Midori all worked okay. Well, except for today when I had problems with all of them over a nornal direct connection via my ISP. So I used Tor to see if I could get to see the site's front page with any browser and found I could and that I could log-in, log-out, and log-in and out, over and over, without problem using all except... ...Google Chrome.
I posted a notification of my problem via Tor and later found I could see the sites's front page using Chrome without an error 500 and log-in via direct connection via my ISP. 15 minutes later I was back to the error 500 in Chrome but firefox and other were working fine. Weird!