Diagnosis
A report is generated from the definitions you make when you specify aquery for the layout of the list. The name of this report always beginswith AQ and the following characters contain information about the usergroup, clients and query itself. These report names are protected, i.e.they are reserved for the query and normally may not be used for otherpurposes.
You tried to create a query with a certain name, but a report alreadyexists with the same name as would be created later on from the query.No query can be created under this name because it would overwrite anexisting report.

Procedure
First check which user owns the report in the message and why he chosethat name. Delete or rename the report if this is possible to avoidrestrictions when choosing your query names. If this is not possible,you cannot create a query with the given name.