To be honest, I don't know what the error message even means.
You normally only get that error under some specific condtions if you directly link to a DLL (without an import library).
I can reprocude the error just writing 'TiXmlText textNode("test");' to a source file and compiling/linking. 'TiXmlElement elementNode("test");' works fine.
I don't know what makes it fail for your plugin, but if you look at
configmanager.cpp, line 992, you'll see that it does work fine for the main app. Hmm... no idea what to say really. :?
Could it be some build flag that's different somewhere? Something like
TIXML_USE_STL or such? Maybe the linker does not find the right function in the import lib for such a reason and then tries to get it from the DLL (which is, by accident, added to the project, too...?)