I was just about to post this myself, I've just spent an hour with bb support.
A couple of sites I use frequently - avforums.com, consumerforums.com would not load, so hopped onto a friends wireless

who has a BT service and low and behold they loaded up fine.
After all the faffing around running tracert, reset modem etc. I was told that a 3rd party was not allowing virgin media traffic accross thier equipment ?????
Yes It's true - thier senior support staff know about it.
I thinks this is the final straw for me with VM.