This may be location specific. It's OK here on Teesside.
Currently it's the same program on 501 and 502, the graphics are exactly the same with no problems. The only difference just now is the sound, one has piped crowd noises and the other doesn't.
Have you guys checked for faults in your area by checking your service status in My Virgin Media.
You can also run a test from there.
Or you could try the Service Status number 0800 561 0061. This often gives details of more local issues down to postcode level.
Dave
The Service you do for others is the rent you pay for your room here on Earth - Muhammad Ali