Sorry to hear of the issues that you've been having a064973. Are you having the same issue with any other channels recordings or just 4 HD?
While this is issue is ongoing, most of the programmes would be available for you to watch on catch up, I know this isn't as convenient as watching a recording but it will ensure that you don't miss anything.
I can't find the program on catch up with Virgin despite it being available on other platforms. However even if it was from what I can see Channel 4 catch up is only in SD which (in my view) looks awful on a large screen TV.
Please could you try to reboot your TV box? If you could turn off the box either on the back of the box(V6 only) or unplug it from the wall, either way please wait 10-20 seconds and turn back on or plug back in.
Hopefully a reset of your box will clear this issue and you can watch the recordings as they should be. If this doesn't help, please let me know and we can look into this further.
Had exactly the same thing on Friday 13/9. By accident I was recording the same 4 HD program on both my boxes at 12.05 midday. They both suffered from picture break up and gaps in the broadcast at the same time. I think this rules out a problem with the equipment. I still only ever see this problem on 4 HD.