sufficient permissions

hello. i have 3 blogs hosted at my site (1 is mine), and whenever i try to login as a subscriber at one of the other two blogs, i get a sufficient permissions error notice.

but, if i go back in my browsing history and go right to the blog i tried to log into, it shows me as logged in. so, this isnt preventing me from logging in, but is giving me a false error. it isnt so much a problem for me as it could be for my bloggers and their subscribers.

anyone know how i can fix this?