Problems stopping SQL6.5 Service

Has anyone got any clues for me about problems I'm having stopping 6.5 mssql service? It happens when our backup software calls a batch file to stop the sql services. Sometimes (1 or 2 times a week) the mssql service will fail to stop. It just tries indefinately till we come in and kill it. Has anyone had problems like this before? The NT event logs hold no clues nor the sql logs. Is there any extra logging I can turn on to reveal the problem it has stopping this service?

net stop mssqlserver

Thanks,

Simon