useradmin error

Hi

would someone happen to know whats causing the following error when I open /useradmin

public com.sap.security.core.jmx._gen.IJmxEntity getAttributeLayoutInformation( java.lang.String uniqueId ) null

There is a bunch of error lines and followed by this:

Current user has user creation permissions in the UME, but cannot create users in the back-end system (data source). The original and possibly untranslated message was: "Not a valid SAP user ID: "YEc7S5efWNHf*3~f$ltL". Reason: SAP user ID must contain at least 1 and at most 12 characters".

Any help is greatly appreciated

Thanks