...a change made during the beta timeframe started requiring you to use a fully specified strong name for such assemblies in your config files. So (for example) something like <channel type="System.Runtime.Remoting.HttpChannel, System.Runtime.Remoting" /> no longer cuts it; you need to use <channel type="System.Runtime.Remoting.HttpChannel, System.Runtime.Remoting, Version=blah, Culture=neutral, PublicKeyToken=blah" />

This doesn't seem to be particularly well documented in MSDN. The examples I've recently been looking at relating to ASP.NET don't include the version, culture, and publickeytoken attributes and so this explains the difficulties I was having.

I'm not sure if there is a better method, but it seems like the way to lookup the values for version, etc. is to browse to C:\WINDOWS\assembly where you can see the assemblies in the GAC together with their attributes.