[MonoDevelop] asp build problem

[Tom Potts]

I've just created a default ASP.Net project and on trying to build/run it I 
get 
System.UnauthorizedAccessException: Access to the path 
"/usr/lib/monodevelop/bin/bin" is denied.
  at System.IO.Directory.CreateDirectoriesInternal (System.String path) 
[0x00000] 
  at System.IO.Directory.CreateDirectory (System.String path) [0x00000] 
  at System.IO.DirectoryInfo.Create () [0x00000] 
  at (wrapper remoting-invoke-with-check) System.IO.DirectoryInfo:Create ()
  at MonoDevelop.Projects.Project.OnBuild (IProgressMonitor monitor) [0x00000] 

even though the project build directory is set to my project tree
How can I fix this?
Tom