[THIN] ICA client failure

I have one user currently that cannot connect to our servers.
He is running Vista, and has local admin rights on his machine.
When he launches the ICA file (either directly from WI, or saved to his desktop) the hourglass pops up for a second or two, but no connection dialog boxes appear.
I remotely attached to his PC and tried to launch this myself with the Task Manager open.   As soon as I launched the ICA file, the wfica.exe appeared in Task manager, and then vanished again within a second or two.
I have Uninstalled and re-installed the Web-only client more than once. I have not yet tried installing the full PN but might try that next.  Any ideas on what is killing the ICA?   I am fairly certain its something within his PC/.