I have had an issue for a while with one of our CRM 4.0 Orgs (that was originally upgraded from CRM 3.0) and now recently had the same problem on a CRM 2011 Org (that was upgraded from CRM 4.0) where I received an InternalOperation error on a native CRM Plugin assembly when trying to add a new user.
I have seen various forum posts around this problem, unfortunately with no solutions.
My team and I spent quite a bit of time investigating this and finally found the solution to the problem (although unfortunately still don’t have the root cause bedded down, that will be the subject of a future post).
The major credit though, needs to go to my Development Manager, Sean Vowles (@seanvowles) who came up with the simple solution.
The Error message goes a little something like this :