CMS 2002 SP1 - Null pointer Errors

[CMSNewbie]

Null pointer errors appear in the Event Viewer when users click around on our
CMS 2002 (SP1) Internet site. We believe it has something to do with the CMS
templates but not 100% sure. Below is the error message we receive:

General Information
*********************************************
Additional Info:
ExceptionManager.MachineName:
ExceptionManager.TimeStamp: 10/8/2009 10:58:50 AM
ExceptionManager.FullName: Microsoft.ApplicationBlocks.ExceptionManagement,
Version=1.0.50607.0, Culture=neutral, PublicKeyToken=null
ExceptionManager.AppDomainName:
ExceptionManager.ThreadIdentity:
ExceptionManager.WindowsIdentity:

1) Exception Information
*********************************************
Exception Type: System.Exception
Message: Object reference not set to an instance of an object.
TargetSite: Void Page_Load(System.Object, System.EventArgs)
HelpLink: NULL
Source: Internet Site

StackTrace Information
*********************************************
at Company.Internet.Controls.PageControls.SiteMap.Page_Load(Object
sender, EventArgs e)

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Has anyone experienced this or know what the problem may be? We have been
troubleshooting and have had no luck due to inconsistent results regarding
the null pointer errors.