I remember running into similar problems when building other packages with recent releases of Qt on Win32. I'm running under cygwin, by the way. After a fair amount of debugging, I discovered that 'qmake' was using the wrong 'mkspec'. One thing that helped this situation was to force the use of the correct mkspec, like so:
export QMAKESPEC=win32-msvc2008
or
export QMAKESPEC=win32-msvc
To find the list of all valid mkspecs, I looked in the directory:
c:\Qt\4.6.0\mkspecs
or
c:\Qt\2010.01\qt\mkspecs
For one particular package, I had some conflicts with other tools installed on my system and had to edit the actual mkspec file to point to the correct tool using an absolute path, but it sounds like that is not your problem here. It sounds like yours is generating a gmake-compatible Makefile instead of an nmake-compatible Makefile, so this fix should work.
-- Glenn