TV-out picture flashes / goes out of sync (1 Viewer)

[tourettes]

I had problems with TV losing sync (flashing black and white / a little bit badly formed picture) for a short period with my NVidia 5200 when :

1) timeshifting was turned on / off
2) channel was changed with timeshifting on

Enabling "Force TV Detection" in Display properties -> Advanced -> NVidia tab -> Tools solved this.