How does one fine tune/dither the dish? My problem is that some HD channels will drop out while I still receive other HD channels. It got bad enough this past Saturday, to where I was 'motivated' to call DirecTV, and after going through the round robin of questions about the weather and what kind of signal strength I was getting, a DTV tech is coming to the house tomorrow. A friend, who has had DirecTV HD a little longer then I have (less than two weeks now) thinks it might be that when the guy installed the 5LNB dish, he 'neglected' to install a multiplexer/multiswitch between the dish and receiver.If your LNB is good, you just need to fine tune (dither) the dish. Also check for bad fittings and low freq. barrels.
It's a good possibility that your B-band converter is either not connected, or is bad.
I am told that you can order a free replacement from DirecTV's website.
Edit: This applies to the OP who has no signal at all on 99 or 103.
I have a slimline 5 LNb with no BBc and get no 99 or 103 but think there may be a problem with 103 that is unrelated to my lack of a bbc. If must have a BBC then that is my problem as my signal levels are in the 97 and up on the other sats