On my install of WordPressMU, running the BuddyPress core plus several other piddly plugins, the Member Access plugin caused two major errors for me:
- Enabling the plugin broke my RSS feed by causing a "missing CDATA close tag" which could only be solved by disabling the plugin.
- When enabled, this plugin caused huge (about 56 MB) core dump files to appear in the WordPress root directory. As soon as I disabled it, the core dumps ceased and all was well.
Of course, it's possible that it's some sort of fundamental conflict between the feed (which is somehow filtered through the BuddyPress plugin methinks) conflicting with the Member Access plugin. Meh, not worth foolin' with. Decided to go with the User Access Manager plugin.