Thanks Ken
Unfortunately that did not help. The error we have been seeing since the 4.0 upgrade is:
Attempt by security transparent method 'CuteChat.RemoteDataProvider.GetPortalInfo(System.String)' to access security critical method 'CuteChat.ServiceClientInterface.RemoteChatServiceFactory.Create()' failed.
Assembly 'CuteChat.AppCode, Version=5.0.0.0, Culture=neutral, PublicKeyToken=caec02264daa66c8' is marked with the AllowPartiallyTrustedCallersAttribute, and uses the level 2 security transparency model. Level 2 transparency causes all methods in AllowPartiallyTrustedCallers assemblies to become security transparent by default, which may be the cause of this exception