Windows Service and WCF Service Problem

I'm implementing a windows service and it contains a WCF client to talk to a
WCF service.  The windows service provides drop-folder functionality for
files so that the files are picked up and processed using WCF services.  I
uses a process scheduler to allocate multiple files to multiple processors
to handle these files.  It all works fine when I test outside the confines
of the windows service.  However, once executed in the context of a windows
service it fails when the WCF service issues a callback to it's client
(which in this case is the windows service) . Then it just hangs.  I'm able
to break into the code and see that is is the callback in the WCF service
that is hanging.  No code has been executed in the client (windows
service).  It could be a permissions issue, but I changed the account of the
windows service from LocalSystem to my user account for testing to see if
that made a difference and it did not.  I'm administrator of the machine I'm
executing both the WCF service and the windows service.

I'm at a loss here to figure out what's going on with this.  This is tried
and tested code (both the WCF client and WCF service) that has worked for
months now and works outside the context of a windows service.  The code and
examples I'm seeing online are utilizing a windows service as a WCF service
but this is not my case.  Is there something I'm missing here to allow it to
work?  Some setting I need that I cannot seem to find?

Any help would be most appreciated.

Thanks,
Mike

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