I'm not able to add new objects (Users, Groups, Computers...) as Administrator anymore.
The problem seems to be more in general. I'm also unable to edit fields in existing entries through the MMC snap-ins. In short terms: I've only read access as administrator.
Created attachment 3675 [details] Patch that fixes the problem
Well found. I wonder how this was got so wrong. Clearly we need a test (in ldap.py) that will find this in future...
This looks like a cut-and-paste bug introduced by 51baa8deec00244cc0a6e3d29c53932427800610 I've applied your patch, well done!
Fixed.