it is either a problem with your network or your server.
1. are you using a wired connection
2. swap the enthernet cable just to rule that out
3. if you are still having problems check your download speeds you should have consistant download speeds of around 1.5 meg
4. if you have checked all the above and it is still not working it will be your service provider i would of thought. you can send me your line and i will test it if you wish.
5. make sure your channel list is upto date.