A web application running in IIS7 on Windows Server 2008 will reject any upload that is larger than 30MB. This is the default size limit for IIS7. To increase the maximum file size, add the following code to <system.webServer> in the web.config file:
(This example sets the limit to 500MB)

<security>
 <requestFiltering>
  <requestLimits maxAllowedContentLength=”500000000″ />
 </requestFiltering>
</security>

You must restart IIS for the setting to take effect.

If you receive this error message from IIS7 on Vista:
An error occurred on the server when processing the URL. Please contact the system administrator

Do the following at the IIS Manager to get a more meaningful message:
1. Select the web site from the tree on the left and click on the “ASP” icon
2. Expand the “Debugging Properties” and set to true the “Send errors to browser”