SerializationException in Web Service

[billa]

Hello,

I am creating a web service with .NET 2.0 and Visual Studio 2005.
I want to enable the following class as a web service:
[WebService(Namespace = "http://webservice.docuware.com/")]
[WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
public class Service : System.Web.Services.WebService
{

[WebMethod]
public string GetStoreDate(string fcGUID, long dwdocid)
{
string date = <do something in an external application and
return a string>;

return date;
}
}
When I now test the GetStoreDate Web Service it actually does
everything right. The debugger shows the correct value for the date
variable. However after leaving the method I get the following
exception:

System.Runtime.Serialization.SerializationExceptio n was unhandled
Message="Type is not resolved for member
'DocuWare.Common.Logging.LoggingContextData,DocuWa re.Common,
Version=5.1.0.265, Culture=neutral, PublicKeyToken=879da714589ba9ea'."
Source="WebDev.WebHost"
StackTrace:
at Microsoft.VisualStudio.WebHost.Host.ProcessRequest (Connection
conn)
at Microsoft.VisualStudio.WebHost.Server.OnSocketAcce pt(Object
acceptedSocket)
at
System.Threading._ThreadPoolWaitCallback.WaitCallb ack_Context(Object
state)
at System.Threading.ExecutionContext.Run(ExecutionCon text
executionContext, ContextCallback callback, Object state)
at
System.Threading._ThreadPoolWaitCallback.PerformWa itCallback(Object
state)
The requested DLL "DocuWare.Common" is referenced in the Web Project
and I also use it in the class:
using DocuWare.Common.Logging;

I am actually not using any classes or methods from the DLL in my
webservice. However it is possible that the some method down the line
from <do something in an external application and return a string> uses
a method of the DLL.

Why am I getting this exception? How can I avoid it?

Thanks for your help.

billa