What exactly do you mean by "crash"? What form does this error message come in; e.g. is it a dialog box or an exception? What events are in the NT application event log? Is there anything suspicious in the speech .etl log files when this occurs? What OS are you on? Is your application doing anything besides executing the speech workflow?
These are some questions to help you narrow down where the problem might be. For more personal assistance than I can give here, please contact our technical support department via http://support.microsoft.com/gp/assistsupport/. If you're in the US you can call (800)936-5800 and ask for support on Speech Server.