I know this problem is old hat by now but I wanted to bring this to your attention and see if I wasn't doing something wrong.
When using Revisionary with Capability Manager enhanced, I receive the Cheatin' uh? error message when attempting to upload and insert images on published pages. The pages were created by an administrator and are being updated by someone with the revisor role that has been given permission to edit others. We are currently using the old version of Capability Manager and are experiencing the same issue.
I noticed that you had fixed this error in Role Scoper but we can't easily use that plugin due to some perceived incompatibilities with other plugins.
Final implementation will be on a WP multisite running 3.4.1.