Please help with Event Type warning

[binici]

Hello, in my event view log for applications, I see quite a few of these messages:
Event Type: Warning
Event Source: ASP.NET 2.0.50727.0
Event Category: Web Event
Event ID: 1309
Date: 11/20/2006
Time: 2:57:01 AM
User: N/A
Computer: PWARDELLIIS
Description:
Event code: 3005
Event message: An unhandled exception has occurred.
Event time: 11/20/2006 2:57:01 AM
Event time (UTC): 11/20/2006 10:57:01 AM
Event ID: e0c00ec8dc224ea0af7ccb2a29e2e191
Event sequence: 1709
Event occurrence: 88
Event detail code: 0

Application information:
Application domain: /LM/W3SVC/824950/Root-1-128084105325727321
Trust level: Full
Application Virtual Path: /
Application Path: E:\Pwr\
Machine name: PWARDELLIIS

Process information:
Process ID: 5636
Process name: w3wp.exe
Account name: NT AUTHORITY\NETWORK SERVICE

Exception information:
Exception type: NullReferenceException
Exception message: Object reference not set to an instance of an object.

Request information:
Request URL: http://www.pwaor.com/_Calendars/cal...1&rcbID=CalendarType&rcbServerID=CalendarType
Request path: /_Calendars/calendar.aspx
User host address: 66.249.66.238
User:
Is authenticated: False
Authentication Type:
Thread account name: NT AUTHORITY\NETWORK SERVICE

Thread information:
Thread ID: 11
Thread account name: NT AUTHORITY\NETWORK SERVICE
Is impersonating: False
Stack trace: at Telerik.WebControls.RadComboBox.x8343762c7247f241()
at Telerik.WebControls.RadComboBox.OnPreRender(EventArgs e)
at System.Web.UI.Control.PreRenderRecursiveInternal()
at System.Web.UI.Control.PreRenderRecursiveInternal()
at System.Web.UI.Control.PreRenderRecursiveInternal()
at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)
I traced the controls, but don't see any problems, What else could I do to troubleshoot this pestering warning?
Thanks for your advice.