WFC Service system.servicemodel.serviceactivationexception

Hi,
just loaded the service on the Winhost site and get this exception when I try and use it. Works from my local machine and from another hosted site in Windows 2003/IIS6 undet dotnet V4.

Have been looking at other sites re the error and no luck. Have tried:

• setting endpoints
• setting windows security
• setting full trust
• setting service reporting

with no luck.
I used the WCF Rest service Template 40 with VS2010 for development. The IIS directory is set for DotNet 4.0
All the web.config adjustments have no effect.

Any ideas?