I'm not sure about your particular recorder but I have a Lite-on DVDR setup to record from cable.
The NTL STB has two scart outputs (at least mine does
) and I have one fully wired scart going to the TV and the second going to the DVDR. The DVDR then has a input scart (from STB) and output scart to TV. When I want to record from cable I have the STB tuned to correct channel and DVDR source set to scart. This works fine, for me.
If you are going STB -> TV -> DVDR are you sure the TV -> DVDR scart is set to Output mode (optional on my Panasonic TV).
HTH