I am running OSX 10.6.6 with xcode 3.2.4. I have been creating c++ source and compiling it with g++ on this machine (successfully) for several months. I haven't compiled anything for a week or two until today; when I tried to execute the binary (which compiled fine), I get a "Malformed Mach-o file" message. I compiled several other source files (that had previously compiled and executed fine) and they also failed with the Malformed message. Binaries that I'd previously compiled continue to execute fine. lipo -info on the (nix) binary returns this message ... Non-fat file: nix is architecture: x86_64 What's the problem and how do I resolve it?