[what?]

i'd advise firstly if its possible to disconnect the router
that'll let u see which device is causing ur problems

if it still happens with the router disconnected
check to see what the lights do on you're modem when it freezes

if they dont change ur gona have trouble convincing ts that there is any fault

also, , since the probs started have u rebooted all the equip?

and has the prob only occured since u went onto 20mb

i'm not sure on teh ntl config pages(though im sure ul find how to access it sumwhere on here)
but theyre worth having a look at to check power levels/ frequency
both of which can cause prob if out of range or near the edge of the range