Same here :
Using 2 tabs in my web browser, one in the admin panel, and the other to check out the website.
If I logout from my user link as if I do using the admin panel logout, the result is the same :
I get logged out from the admin panel, which is exactly what we expect doing so, but the
is_user_logged_in() seems to stay true as in the website tab, I stay logged in...
This happens to me since WP-members has a locale translation (fr_CA). I had to uninstall it and reinstall it as some fields were not getting translated, and dropped the related db tables to be sure, but now, with a clean WP-members install, using french language, there's no way to logout form the user website.
Help please :)