Hi
I have had the same issue for months! the hosting company say they cannot find an issue and NTL support have supposedly opened a ticket with the network team

(2 weeks ago and still no contact from NTL).
what happens is Outlook Express which checks email at 10 min intervals reports an error despite my ntl and other email accounts working fine then a quick check and
www.mds.cc shows server not found. (not much to see there but i use the email alot). I can go to other sites like google etc no problem.
tracert stops because of a firewall but as i pointed out the routing dies 1 hop before the firewall. I would expect NTL to have enough power to talk directly to the operater of the IP/router or whatever it is that dies (cable internet) to find out why packets fail to get thru at random.
Using my 0845 dial-up (ISDN non NTL) i get thru ok.
Kram
On NTL BB from Leeds via STB (Pace)