So you have used update panels before.  And the same code you may have used in an AJAX enabled website does not work when you put it into a Web Application. 

I struggled with this for several hours before discovering that if you have the following line in your web.config file it breaks ASP.Net AJAX.
<xhtmlConformance mode="Legacy"/>

I have not researched the reason behind this but I plan to do so and will provide an update when I find more information.  Just know that you can comment out this line or change the mode from Legacy and your Update Panel should start working.  Let me hear from you if you know why this breaks ASP.Net AJAX or if removing this config entry does not clear your problem.

UPDATE: 2/5/2008

Found that this config file entry is created when migrating from VS 2003 to VS 2005 and can occur with Web Applications and Websites.  For a deaper understanding Scott Guthrie sheads some insight.

So you are trying to modify the Reporting Services CSV export behavior.  This article will outline two specific behavior changes:

• How to turn off exporting of the header record
• How to change the encoding to ASCII

By default Reporting Services exports a CSV file encoded as Unicode and contains a header record.  Lets start with turning off the header record.

 NOTE: make a backup of any config file prior to making any modifications.

1. First determine the Instance ID of the Report Server for which you want to make the change.  You can do this by opening the Reporting Services Configuration Manager: All Programs - Microsoft Visual Studio 2005 - Configuration Tools
   Then connect to the appropriate instance.  With server status selected on the left you will see the Instance properties.  The Instance ID will be used in locating the config file which needs to be changed.
   
   
   
   
2. Locate and open the rsreportserver.config file with a text editor.  C:\Program Files\Microsoft SQL Server\MSSQL.2\Reporting Services\ReportServer\rsreportserver.config 
   Replacing my MSSQL.2 with your Report Server Instance ID.
   
3. Locate the config section: <Configuration><Extensions><Render>
   
4. Find the <Extension> config entry.

   <Extension Name="CSV" Type="Microsoft.ReportingServices.Rendering.CsvRenderer.CsvReport, Microsoft.ReportingServices.CsvRendering" /> 

    
5. Extension default behaviors can be modified by making appropriate entries in the device information settings.  So to exclude the header row from the output:
   

   <Extension Name="CSV" Type="Microsoft.ReportingServices.Rendering.CsvRenderer.CsvReport, Microsoft.ReportingServices.CsvRendering">

       <DeviceInfo>

           <NoHeader>true</NoHeader>

       </DeviceInfo>

   </Extension>

    
6. So now if you want to also change the encoding to ASCII simple add the Encoding device information setting:
   

   <Extension Name="CSV" Type="Microsoft.ReportingServices.Rendering.CsvRenderer.CsvReport, Microsoft.ReportingServices.CsvRendering">

       <DeviceInfo>

           <NoHeader>true</NoHeader>

           <Encoding>ASCII</Encoding>

       </DeviceInfo>

   </Extension>

    
7. Save the file.

There are also other device information settings for the CSV Rendering Extension.  You can change the Field Delimiter, Record Delimiter, change the file Extension and more.  Here are the CSV Device Information Settings.