Users with DB2 v9.5 or DB2 v9.7 can experience a crash of AQT when they hit the Abort button to cancel a query.
This is a problem with the DB2 Client that is described in APAR IC66407 - see http://www-01.ibm.com/support/docview.wss?uid=swg1IC66407
The problem is fixed in DB2 v9.5 fixpack 6 and DB2 v9.7 fixpack 2.