Hi,
Couple of things you could try,
first option, shutdown your modem/set top box, then scan your pc for spyware/viruses and clean as necessary and reboot if required. Next, power up your modem/set top box and see how that goes.
second option, use a restore point from say, three weeks ago and again, scan your pc for spyware/viruses and clean as necessary.
third option, assuming the first two didn't fix things, if you have virgin's cable services, try ringing 151 and you can talk to the tech support for free. If you don't have virgin's cable service, you could ring 0845 454 1111
this link
http://status-cable.virginmedia.com/vmstatus/summary.do will tell you of any known issues with virgin's cable services (when your connection is working).
hopefully, these will help restore your services to full working order, if not, then i'm sure one of our more techy members, wil be able to think of something to help.
Ray