Linking error: ../Control/MessagingSystem/libMessagingSystem.so: undefined reference to `opencog::messaging::MessageCogServer::getID()'

Linking CXX executable pbTest
libPBTester.a(PBTester.cc.o): In function `~PBTester':
/home/dhart/opencog_trunk/src/opencog/embodiment/AutomatedSystemTest/PBTester.cc:52: undefined reference to `opencog::messaging::MessageCogServer::~MessageCogServer()'
/home/dhart/opencog_trunk/src/opencog/embodiment/AutomatedSystemTest/PBTester.cc:52: undefined reference to `opencog::messaging::MessageCogServer::~MessageCogServer()'
libPBTester.a(PBTester.cc.o): In function `PBTester':
/home/dhart/opencog_trunk/src/opencog/embodiment/AutomatedSystemTest/PBTester.cc:48: undefined reference to `opencog::messaging::MessageCogServer::MessageCogServer()'
libPBTester.a(PBTester.cc.o): In function `AutomatedSystemTest::PBTester::init(std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, int)':
/home/dhart/opencog_trunk/src/opencog/embodiment/AutomatedSystemTest/PBTester.cc:66: undefined reference to `opencog::messaging::MessageCogServer::setNetworkElement(opencog::messaging::NetworkElement*)'
libPBTester.a(PBTester.cc.o):(.data.rel.ro._ZTIN19AutomatedSystemTest8PBTesterE[typeinfo for AutomatedSystemTest::PBTester]+0x10): undefined reference to `typeinfo for opencog::messaging::MessageCogServer'
libPBTester.a(PBTester.cc.o):(.data.rel.ro._ZTVN19AutomatedSystemTest8PBTesterE[vtable for AutomatedSystemTest::PBTester]+0x38): undefined reference to `opencog::messaging::MessageCogServer::customLoopRun()'
libPBTester.a(PBTester.cc.o):(.data.rel.ro._ZTVN19AutomatedSystemTest8PBTesterE[vtable for AutomatedSystemTest::PBTester]+0x148): undefined reference to `opencog::messaging::MessageCogServer::sendMessage(opencog::messaging::Message&)'
libPBTester.a(PBTester.cc.o):(.data.rel.ro._ZTVN19AutomatedSystemTest8PBTesterE[vtable for AutomatedSystemTest::PBTester]+0x150): undefined reference to `opencog::messaging::MessageCogServer::sendCommandToRouter(std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)'
../Control/MessagingSystem/libMessagingSystem.so: undefined reference to `opencog::messaging::MessageCogServer::getID()'
collect2: ld returned 1 exit status
make[2]: *** [opencog/embodiment/AutomatedSystemTest/pbTest] Error 1
make[1]: *** [opencog/embodiment/AutomatedSystemTest/CMakeFiles/pbTest.dir/all] Error 2
make: *** [all] Error 2

Seeing this error on Shujing's machine, and mine.