error message: an outgoing call could not executed because it forwards a synchronic entry call

An application that communicates itself internally with a DCOM-Server should
be able to be closed from another application with a SendMessage and a
WM_Close. This should work, in principle, but an Error message appears:

<an outgoing call could not executed because it forwards a synchronic entry
call>
(this is a translation from german, I hope it is the same error-message!)

The same error message appears when the right mouse button is clicked on the
task bar, but only the first time this is done.

Does anybody have an explanation or, rather, a solution?

thank a lot,

Frank (GmbH)