Calendar exception

[Tgaud]

Hi, we are running Telerik on a security test tools which use Http request manually to bypass the GUI and javascript control.
(To simulate a hacker)

And we have a Telerik exception on radcalendar :

Here is the Log :
--------------------------
Thread information:
    Thread ID: 6
    Thread account name: NT AUTHORITY\NETWORK SERVICE
    Is impersonating: False
    Stack trace:    at Telerik.Web.UI.RadDateInput.RangeTextProperty(String value)
   at Telerik.Web.UI.RadDateInput.set_Text(String value)
   at Telerik.Web.UI.DatePickingInput.LoadPostData(String postDataKey, NameValueCollection postCollection)
   at System.Web.UI.Page.ProcessPostData(NameValueCollection postData, Boolean fBeforeLoad)
   at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)
------------------------------

There were an incorrect date input forced in the HttpRequest to the server who create an error.

How can i prevent it from happening ?
How can i manage this exception ? I have no clues and i really dont understand what happens.

[Tgaud]

I've activated the "classical" mode in IIS 7.0 instead of "integrated" and now the application isn't crashing anymore.
Maybe it's a consequence of the telerik httphandler in the webconfig's IIS 7.0 section ?