Just thought I would pass on my experience of sorting out the cache/proxy problem..
I was having a real problem trying to reach a site at
www.exampleshop.co.uk.
Whenever I tried to go this site I kept getting server unreachable and the trace route couldnt even resolve the name to begin its job.
Yet whenever i contacted someone else to try they had no problems connecting to the site at all - as far as they were concerned there it was just sitting there.
Changing to a specified cache server didnt help and the logs showed different NTL cache servers were used at one time or another anyway.
Eventually i ended up looking at the excellent sticky about changing DNS and proxy servers at:
http://www.cableforum.co.uk/board/showthread.php?t=8783
and thought well if NTLs nameservers cant find the site through its caches then no one elses are going to.
Sure enough when I changed the nameserver entries on my machine to NTLs nameservers - bingo and no problems since. The nameservers are 194.168.4.100 / 194.168.8.100
So if anyones having the above problems then changing to NTLs nameservers as per this sticky should - IMHO - be the first thing to try.
HTH
