Problem with 2.4.7.1 | Add Ip-Address

[Achmed]

Hi,
i have a problem with 2.4.7.
Today i wanted to add another IP.
Logged in as admin, went to "Manage IPs", added new IP with domain and alias, no problem.
Switched to "Edit reseller", checked the new IP and tried to update:
Undefined user accounting error!
Nothing to find in the logfiles.
I think the problem is, that i already have a user with the domain i assigned to this new ip.
What can i do?
I don't want to delete this user if its not necessary.

Sorry for my bad english