Upload & Sell: Off
That is odd. The only thing I can think of is that the optical sensor isn't being cut out when the radio trigger is plugged in, and a doubled sync signal is locking it up. To rule that out, try putting a piece of black tape over the optical sensor on the problem head and see if it then works with both strobes firing.
Many thanks,you are a clever guy,that has sorted the problem out,much obliged wouldnt have thought of that myself,knew I was a bit dim