as to CDN, again it depends on the implementation... if it thinks it can do things specifically for WP, like cache a wp page, it may work incorrectly since a single WP page is used for a forum display... the appearance of many pages is simple url rewrite magic... fundamentally, CDN can work and we have users that use forms of it...
you could try a simple test and turn it off or clear and see if things clear up..
Visiting and/or updating a user profile in admin wont affect which forums you can access at all... but it could affect a cache...
obviously, I cannot sit here and says its a caching issue, but its acting like one... and user permissions wont be affected by a profile update - they are completely separate - admin capabilities in the backend could, but that is not the issue here... there is really no way for permissions to get out of whack and then self correct (including by profile update)... some overt actions in the admin (like modifying a permission or forum or housekeeping panel actions) but not an admin profile update (that is wp territory)...
will keep the accordion issue in the other topic...