Hi, I have a simple "Hello World" GUI app, which uses Windows.Forms. Using the official Mono installer for Mac OS, the applications works fine. Due to problems with compiling additional packages like gtk- sharp, I decided to try the Macports version of Mono. A sample command line application works fine, but my GUI sample fails with the following message: Unhandled Exception: System.ExecutionEngineException: SIGILL at <0x00000> <unknown method> at (wrapper managed-to-native) System.Diagnostics.StackTrace:get_trace (System.Exception,int,bool) at System.Diagnostics.StackTrace..ctor (System.Exception e, Int32 skipFrames, Boolean needFileInfo, Boolean returnNativeFrames) [0x00000] at System.Exception.get_StackTrace () [0x00000] at System.Exception.ToString () [0x00000] at System.Exception.ToString () [0x00000] at System.Exception.ToString () [0x00000] at System.Exception.ToString () [0x00000] at <0x00000> <unknown method> at <StartupCode>.Forms._main () [0x00000] Any hint what might be wrong? regards, Achim