Would need to look at the exec plan to say anything useful. Could be a bad execution plan for one reason or another and the query is just running and running.
Async network IO is usually an application problem, maybe take this up with whoever developed the system that is running the query.
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability