I got this error after installing the Mono framework on MacOS X 10.5.6 and trying to set up a new project with eclipse. NAnt 0.86 (Build 0.86.2898.0; beta1; 12/08/2007) Copyright (C) 2001-2007 Gerry Shaw http://nant.sourceforge.net For more information regarding the cause of the build failure, run the build again in debug mode. Try 'nant -help' for more information BUILD FAILED Failed to initialize the 'Mono 3.5 Profile' (mono-3.5) target framework. Function call failed.