I was getting the above error on a plugin that was making use of CreateAttribute request class. The plugin was registered on pre-operation Create event.
From the error message it seemed that we cannot use CreateAttribute request message as a part of same transaction in which the plugin was already running. So we tried by registering our plugin in Pre-Validation stage i.e. outside of transaction. (as used to be the case in CRM 4).
This way I was able to resolve the issue.
Hope it helps.