I get this error too, but it affects the front end too. I’m using WordPress 3.3.2. BuddyPress Version 1.5.5
The error made it difficult to uninstall the plugin too – had use the file browser to go into wp-admin/plugins/ and delete the invite-anyone folder (just in case anyone is stumped). WordPress gave a little message saying the plugin had been deactivated because the files were gone, but all seems to be working now.