I recently installed the mono-1.2.5 package. The mono command works OK, but the mono C# compiler, mcs, dies with "Bad system call". I was wondering if it works for you and it's a problem with my system, or if the package is broken.
(If you dont have any C# sources, you can try the hello-world example at http://www.mono-project.com/Introduction_to_developing_with_Mono)
I am trying right now to rebuild from the cygport sources, but it's slow going. I also have the older mono-22.214.171.124 package which gives me the same problem.