I have updated my daily build site with the new development tools (mingw-mame-w32-20120807.exe) and I have this error when doing "c:\mingw\mingw64-w32\bin\make TARGET=mess" :
Compiling src/osd/windows/vconv.c... cc1.exe: internal compiler error: Illegal instruction Please submit a full bug report, with preprocessed source if appropriate. See <http://gcc.gnu.org/bugs.html> for instructions. make: *** [obj/windows/osd/windows/vconv.o] Error 1
vconv.c is the very first file trying to be compiled. So in fact cc1.exe does not work at all.