RGB connections ??

Here's one for all you techies.
Just purchased aLoewe Aconda with the matching video and DVD
Very pleased with them so far.Pictures great and they are right when they say its nice to look at with the set off.!!

Anyway,there are three scart sockets on the TV
The instruction manual says that the DVD must go on Scart 3,the video to scart 1 and this leaves the NTL Cable box to go on to scart 2.As it happens Scart 2 is the only one that is marked with RGB although i thought i had read a review saying they were all RGB compatible.When i change the Cable options to produce RGB this works ok,but when i switch back to BBC1 on the normal channels the picture is completely skew whiff.
I know i could just use the cable to change channels but it then renders the Teletext inoperative.
Any ideas on this one
Thanks
Percy