I have found two issues in Net/src/NetworkInterface.cpp that I believe to be bugs:
l.51: #include "Poco/Error.h" is done only if we have POCO_WIN32_UTF8[ - but it is needed also on Windows machines without Unicode. It helped to move it one line down, i.e. after the #endif.
l.1025: rc is used here, but it is declared first on line 1028. The solution is to move its declaration ("int") from line 1028 to line 1025.
(This is weird, since this was OK in version 1.5.)