Setting maxJsonLength property for UpdatePanel

I have a third party grid (componentArt Grid) on an update panel. And, I am loading data to this grid in a partial postback but I get following error when I try to load more than 2000 rows to the grid. This is not a restriction coming from the grid but it seems to be happening because of partial postback in update panel.

Error is: |Error during serialization or deserialization using the JSON JavaScriptSerializer. The length of the string exceeds the value set on the maxJsonLength property.|

I updated web.config to set the maxJsonLength property but it seems to be ignored. I am using .NET Framework 4.0 and IIS7. I see an article in Knowledge Base that describes same issue for .NET Framework 3.5 and has a hotfix for it but I don't see anything for .NET Framework 4.0.

I would appreciate any help in this.

My web.config setting is -

<system.web.extensions>
    <scripting>
      <webServices>
           <jsonSerialization maxJsonLength="2140000000" />
      </webServices>
    </scripting>
  </system.web.extensions>

Thanks,

Sangeeta