ASP/Web Application Error

I'm running an asp application running on windows2003 server,with microsoft office and ms SQL installing on the server. Recently when I run my web application, I get the following error. The sstem use to print out the result in a excell spreadsheet.


The server process could not be started because the configured identity is incorrect. Check the username and password.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.Runtime.InteropServices.COMException: The server process could not be started because the configured identity is incorrect. Check the username and password.

Source Error:

Line 244:                '---> Launchs Sub to Execute Create Report
Line 245:                StartTime = Now
Line 246:                oExcel = New Excel.Application
Line 247:                ExecuteCreateReport()
Line 248:                Dim EndTime As String = Now

Source File: C:\Inetpub\wwwroot\ASPForecast\Reporter.aspx.vb    Line: 246

Stack Trace:

[COMException (0x8000401a): The server process could not be started because the configured identity is incorrect.  Check the username and password.]
   ASPForecast.Reporter.Page_Load(Object sender, EventArgs e) in C:\Inetpub\wwwroot\ASPForecast\Reporter.aspx.vb:246
   System.Web.UI.Control.OnLoad(EventArgs e) +67
   System.Web.UI.Control.LoadRecursive() +35
   System.Web.UI.Page.ProcessRequestMain() +750

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Version Information: Microsoft .NET Framework Version:1.1.4322.2300; ASP.NET Version:1.1.4322.2300