Help with impersonation in referenced DLL

Hi,


I've been struggling with this serveral days now.
Scenario:
I have a webservice where I have two Logging methods. The webservice references a Logging framework we have coded ourselves. 
The logging framework has a config file where a connectionstring to a database is configured. This connection string is using Trusted_integration=true.
When calling this method it fails to execute the insert command in the databse with this error: Access denied for user [domain]\[Servername]$.
The webservice itself is impersonated to a serviceaccount. All methods in the webservice are working fine (with the correct user), but the two methods that are logging through our dll are both failing with the error above.
Can anyone explain why the DLL is being run as [domain]\[Servername]$ and not the serviceaccount that I specified i the webservices web.confg? And how to force the DLL to be run under the serviceaccount user?
Regards,
Kenneth