Here is the error copied from the event log. Could you please let me know what causing this error? Thanks.
 
=Event Type: Error
=Event Source: SLAM
=Event Category: None
=Event ID: 0
=Date: 6/8/2010
=Time: 11:44:50 AM
=User: N/A
=Computer: VM219
=Description:
=System.NullReferenceException: Object reference not set to an instance of an object.
= at AWS.SLAM.ListItemEventManager.<>c__DisplayClass14.<ItemDeleting>b__10()
= at Microsoft.SharePoint.SPSecurity.CodeToRunElevatedWrapper(Object state)
= at Microsoft.SharePoint.SPSecurity.<>c__DisplayClass4.<RunWithElevatedPrivileges>b__2()
= at Microsoft.SharePoint.Utilities.SecurityContext.RunAsProcess(CodeToRunElevated secureCode)
= at Microsoft.SharePoint.SPSecurity.RunWithElevatedPrivileges(WaitCallback secureCode, Object param)
= at Microsoft.SharePoint.SPSecurity.RunWithElevatedPrivileges(CodeToRunElevated secureCode)

= at AWS.SLAM.ListItemEventManager.ItemDeleting(SPItemEventProperties properties)

=For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp.