This is also happening for me and I do not have the role manager installed (I don't think anyway), in fact, UAM is the only type of manager I have installed (others are Twitter, Code Colorer, and things like that).
I tried changing write access from "only group users" to "all", but that didn't help.
I want it so users can write into any category, write public posts or flag a post as viewable by a certain group only, and be able to login from outside the IP to view those posts (assuming they are part of the group).
All is good except for being able to write into any category. If I add all categories into the UAM group that is set up, all posts are flagged as visible by that group only.
Hope this makes sense and this gets fixed soon...