gfxASurface and Win32 friends

Is there some mozconfig option which stops these classes being included 
in libraries? The .obj files are definitely in ..\build\gfx\thebes\src 
but I'm getting linker errors (edited example below)

: error LNK2019: unresolved external symbol "__declspec(dllimport) 
public: void * __thiscall gfxASurface::GetData(..)
: error LNK2019: unresolved external symbol "__declspec(dllimport) 
public: void __thiscall gfxContext::Paint(double)"
: error LNK2019: unresolved external symbol "__declspec(dllimport) 
public: void __thiscall gfxContext::SetSource(class gfxASurface : error 
LNK2019: unresolved external symbol "__declspec(dllimport) public: 
__thiscall  gfxWindowsSurface::gfxWindowsSurface(..)

Or, alternatively, is this a typesafe linkage error?

Google has one reference to the same problem but, sadly, no solution. 
Any help appreciated.

Thx.

Jerry