@spirantho
If switching connectors doesn't work, maybe between us we can find something else wrong, but if it works with your TV it's probably your VCR that's misbehaving... or you're using it wrong. 
Thanks for the reply. I think I tried swapping connectors at the time. I think it may be the VCR. I wondered if it was a macrovision problem, that for some reason the auto gain control wasn't kicking in. But knowing how macrovision works, that doesn't really make sense (does it?).
But then what really makes me think it's a vcr problem (and maybe macrovision related) is that i'm unable to watch my dvd played through the vcr scart sockets either - i get the MV light-dark screen effect.
Annoying.
Martyn.
