ASP.NET UpdatePanel Works in VS2010 Development Server but not IIS 6

I have a Visual Studio 2010 project which targets v4.0 of the .NET framework.

In the project, I have a page with an ASP.NET UpdatePanel - which works perfectly within VS2010's development server.

However, when deployed to an IIS 6 server, the controls in the UpdatePanel cause a full-page postback - not an async p开发者_开发技巧ostback.

The site has its own application pool.

I've tried visiting the ScriptResource.axd URLs which are present in the rendered page and they all produce valid looking JavaScript files.

I can't see any Javascript or other errors.

PLEASE help me debug this! I've got to get this site live tonight!

OK - Just fixed it.

It turns out my live server had a slightly older version of .NET 4 installed. I updated to the latest 4.0.30319 and it started working!