[Marco van Herwaarden]

Check the cookie settings using tools.php and reset if needed.

Moderators gettings into an admin account could indicate a bad configured proxy server that delivers cached pagews to the wrong connection.

Bad configured load balancer or such could also be the cause of some of these problems.

If none of the above, check your .htaccess rules if any and finally turn off modifications, ensure you have only original files and try with a default style.