I login to the board. I go to a profile, administer user, admin login, it logs me into the ACP and puts me on a manage user page instead of the users administrate page. Seems to be losing the user id for the user I'm trying to administrate. It works fine, when using the Administer link once I have an ACP session.
I didn't notice it till now since we updated to 3.1.x, since I usually login, then acp login. then go about my business.