Dear all,
We have the same issue - no chance to log in since release 1.7.6.7 (our hoster skipped 1.7.6.6). Tested a lot of the old BO / admin page solutions provided on the web but nothing worked. No clue. I contacted my hoster to see if they have found a resolution as we got automatically upgraded by them but also to inform them to stop the automated upgrade (as we would like to make a fallback).
.htaccess was changes but I don't know... deleting cash did not help, deleting cookie did not help and so on. I even did check some of the coding part but did not see what was wrong. I just found out whilst checking ps_employee that I never was logged in even I entered all the credentials and clicked login. Checked with several browsers, computers.
Cheers,