[MonoDevelop] MAC after Monodevelop install X11 connection from client no longer works

[andy]

On a mac.
I develop on virtual machines such as ubuntu and don't run window 
managers on them but when I need to I do an "xhost +" on the mac and run 
X11 clients displaying on there.  Since installing Monodevelop this no 
longer works - attempts to start a client displaying on the mac X11 give 
"Xt error: Can't open display: %s".  Checked X11 security preferences - 
no probs there.

This is a bit of a disaster for me as it prevents me from working - can 
anyone help ?

My guess is either Monodevelop has changed a setting in some preference 
place or that its finding something belonging to Monodevelop earlier in 
the path but these are only guesses.

Complete panic - can't revert to backup, too much work since.

andy