I’m having same issue regarding login returning to login page under Multiple Site Manager. Curiously, I’ve seen a few threads this month on the same. And behavior seems to be “special” under MSM.
I have no problem getting to Control Panel in Safari or Firefox on a Mac, by the way. But only Safari will work on Windows. IE, Firefox just reload login page every time.
I was able to finally get login to Control Panel working on Windows machines by changing security preferences to SessionID only. BUT, only default site control panel will load. If I try to select an alternate site, I am simply returned to the default site control panel.
I’ve tried all combinations of SessionID, Cookies and mixtures on preference page for both the default site and alternate site. No luck.
I’m running 1.6.3