Hi James,
I have always suspected the config settings but must have tried most of the permutations by now ! The settings as at the last failed test were:
oscillator XT (whilst I have the resonator in circuit)
power up timer is enabled but nothing else under the config menu
i.e.Watchdog timer,Brown out reset lvp Flash program write are all disabled
Can't see any reference to mclr but I do have 1K to +5 voltson pin 1
Thanks for the suggestions
Cheers
David