This is an ongoing problem with several websites. They are all either 2.6 or 2.7. I had hoped updating to 2.7 would fix it....
I've tried so many different methods of upgrading and fixes.
Moved the plugin folder, logged in, moved it back. Works sometimes or for a while, then back to the reloading log in page.
Taken out one plugin at a time (can't deactivate if I can't log in) and thought I'd narrowed it down to one. But a few hours later, same problem.
Did the re-do of the md5 hash. No change.
Sometimes I go to the admin area (via bookmarked link) and can get in. then when I click something, I am kicked to the log in page. Other times, I can't even get to an admin page. Or I'll get in and be halfway through a post when it will say "cannot save draft since you aren't logged in" (or something like that).
Very frustrating. Very annoying.
I've been using WP for over 4 yrs and have never had this much trouble. Heck, very little to no trouble at all!
I've tried another computer. At first, I could log in then it started the problem there, too. I'm wondering if it is a Firefox issue. I was just able to log in using IE (shudder). Someone please find a fix for this so I won't have to use IE again.