Live TV channel change problem

[lost@c]

First post so please go easy on me. I have searced for an answer to this but no joy so far.
When I watch live TV and change to a channel that requires a change of LNB (through my 2 way switch) it takes about 20 secondes and then shows a black screen with the strength meter at 0 and asking me to check my cables etc. If I then change to another channel on the same lnb it works ok then if I switch back the the 1st it now works ok. I never get the problem when recording, only live TV.
I was suspicious of my cards (HVR-3000) ability to swap between LBM's and polarities but using Wintv or Progdvb I don't get the problem. Any thoughts?

[sub]

I've seen another couple of users comment about having this problem in the past, but I wasnt able to reproduce it here when I tried. I'm not really sure what to suggest on this one.

[lost@c]

It's as if the DISEQC signal is not long enough during the change. As I said the recordigs are fine so I can live with it if necessary.