Unable to assign User groups in Enterprise Portal

Hi,

We are using EP 7.0 with MS SQL on Windows 2003 Server. Recently we have changed the UME to IDES EHP4 System. We can able to create users in the backend system and can read but when we try to assign any groups to the user we are getting the following error,

User attributes successfully modified

You are not authorized to assign one or more entities. Perform a new assigned entities search to see the correct status.

I am the administrator with full rights. Please help us, what is need to be done to resolve the issue.

Thanks,

Ajay.