Thanks for the reply. I'm still stuck on this, so help would be appreciated.

>Have you built Boost with the new compiler/settings?

I'm attempting to migrate the app from 32 bit from 64 bit, so yes. However, I'm trying to link against a 64 bit version of boost, and it's not just boost where I get linker errors, it's everywhere...

1>main_window.obj : error LNK2001: unresolved external symbol __imp_CloseHandle
1>dogma.lib(file_utils.obj) : error LNK2001: unresolved external symbol __imp_CloseHandle

domga.lib is my own library. I have both 32 bit and 64 bit builds of this and have no problem building non-QT consolve apps against either version. Why can't I build a QT app against it, where previously the 32 bit version built fine?

Clearly I'm missing something with the QT pro file, like something switch that says "64 bit" or something that should be completely obvious, but just isn't to me.

How can I track this down?