bp2411, if you have a look at this sticky (
http://www.cableforum.co.uk/board/12...al-levels.html) it tells you the optimum power levels.
I would say that looking at your power levels they are right on the edge of the optimum levels but coupled with the T3 time-outs your router is having difficulty holding it's connection. Therefore I would recommend you call VM (151 if you have a VM phone) and report it as a fault so they can send a tech out and adjust your signal levels.
Good luck and let us know how you get on.