[Dean]

Sorry, guilty as charged, here's a bit more information. Your help is appreciated folks, it's driving me mental.

How do you re-connect?
I have to sit it out, pulling the plug sometimes gets me back, sometimes not. Coming back after pulling the plug works 40% of the time. Even if I come back, I'll be in a 20 minute ish wide window of disconnections.

What hardware are you using? Router, usb etc...
Direct connection over ethernet. If I plug in the GF's laptop after resetting everything, I get the same problem, Sync light on, no data getting to the modem.

What are the logs on the modem saying?
First Time Last Time Counts Level ID Text
Time Not Established Time Not Established 2 Critical(3) 68000300 DHCP WARNING - Non-critical field invalid in response.
Sat Apr 21 14:27:57 2007 Sat Apr 21 14:27:57 2007 1 Critical(3) 82000500 Started Unicast Maintenance Ranging - No Response received - ...
Time Not Established Time Not Established 4 Critical(3) 68000300 DHCP WARNING - Non-critical field invalid in response.
Time Not Established Time Not Established 1 Critical(3) 82000500 Started Unicast Maintenance Ranging - No Response received - ...
Time Not Established Time Not Established 3 Critical(3) 68000300 DHCP WARNING - Non-critical field invalid in response.
Time Not Established Time Not Established 1 Critical(3) 82000200 No Ranging Response received - T3 time-out
Time Not Established Time Not Established 1 Critical(3) 68000300 DHCP WARNING - Non-critical field invalid in response.
Time Not Established Time Not Established 2 Critical(3) 82000200 No Ranging Response received - T3 time-out
Time Not Established Time Not Established 1 Critical(3) 68000300 DHCP WARNING - Non-critical field invalid in response.
Time Not Established Time Not Established 2 Critical(3) 82000200 No Ranging Response received - T3 time-out
Time Not Established Time Not Established 1 Critical(3) 68000300 DHCP WARNING - Non-critical field invalid in response.
Time Not Established Time Not Established 2 Critical(3) 82000200 No Ranging Response received - T3 time-out
Time Not Established Time Not Established 2 Critical(3) 68000300 DHCP WARNING - Non-critical field invalid in response.
Thu Apr 19 17:51:43 2007 Thu Apr 19 17:51:43 2007 1 Critical(3) 82000500 Started Unicast Maintenance Ranging - No Response received - ...

What are your signal levels?
They are within Docsis spec, the one thing I notice though is that as soon as I notice a disconnection, if I'm able to get to the modem info screen, my upstream is between 56-59dB

Here's what I've tried so far:
Replaced cable modem (NTL sent another).
Tried running CM off USB to eliminate problems with my ethernet driver.
Deleted my Norton firewall and virus scanner.
Deleted and fully reinstalled my tcp/ip stack.
Patched tcpip.sys to allow more than 10 connections/second.
Switched off central heating in case power spikes are fubaring the CM
Swapped all internal cables.
Run CM without conditioning filters.
Put CM out the window to keep it cool.
Opened CM and added heatsinks + 1.5 inch fan powered by PC.
Turned off moblile phone.
Turned off cordeless phone.
Put wireless radio thermostats into the microwave oven to isolate them from the house.
Connected CM to downstairs connection point.
Dremmeled a load of corroded grime off main cable feed to house.
Disconnected TV and digibox from cable feeds.
Swapped CM PSU, and plugged it into a seperate socket.

The main feed was open to the elements when I moved in 6 months ago, the f connector on the main feed from under the street is heavily corroded.more info
The CM is a ntl 250