Bonc -
+ What O/S are clients trying to execute the batch file? And I assume no problems re: security rights to access the share?

+ Was this a typo: "I've tried the %comspec% cmd /c, start and without."? You would use either '%comspec% /c' or 'cmd /c', but not both on one line.

+ Does you batch file require a mapped drive to execute, versus UNC naming?

Bill