AVR-Chat

I've got two new Mega168 boards which I'm trying to program via STK500/ISP 
but the STK500 doesn't appear to be talking to the AVR - "Entering 
programming mode .. FAILED!" on Read Signature. This is the first time I've 
tried to use the STK500 for ISP - used to use an Equinox serial/parallel 
programmer but it doesn't support the 168. The new boards have minor changes 
from a previous Mega8 design - the STK500 will talk to the Mega8, so that 
much of it is working and suggests there's nothing fundamentally wrong with 
the circuit.

The 168's are samples direct from local supplier and I assume should be in 
default/unprogrammed state. Clock (external 16MHz xtal) isn't running but I 
guess it won't until the relevant fuses are set? This is the first time I've 
had to use a SM AVR and I can't remember if I've previously had to parallel 
program the Mega8's before I could use ISP. Should I not expect to be able 
to do ISP from scratch? Could it be the external xtal that's the problem?

Thanks,
Mark