I was watching the snooker on BBC2 tonight and had Eastenders set to record on BBC1. When the recording started I could no longer watch BBC2.
I have a quad LNB fitted to the dish and the cables connected to the correct connexions on the Humax box.
Could it be that I have connected to the wrong outputs on the LNB or would that not matter.
I thought that I could watch one program and record another, but have I got something wrong?

The outputs don't (shouldn't) matter.

Try a factory reset of the Humax box - have you ever used it with just 1 cable form the LNB?

Two things to check.

1) Have you got the dish connected to the right inputs on the back of the HDR? An easy mistake is to connect one of the leads to LNB1 Out rather than LNB2 In.

2) If the box was first used with a single LNB connection (which could be due to a mistake as above), it needs to be reconfigured before it recognises that it has two connections. The easiest way to do this is with a Factory Reset (Page 55 of the manual). You will need to reschedule recordings following the reset, but existing recordings will be unaffected.

Thanks guys. The box was used with one LNB input as it arrived before the dual LNB and I didn't realise that I had to do a factory reset after connecting both feeds.
Will do it in the morning.