Just cancelled my UPC today (1 months notice required). we had what sounds like that exact problem, but it became continuous. Wireless on laptop working perfectly (we're currently picking up a neighbours) but our UPC is not. Called them and they blamed the wireless which is Netgear and they will not service a fault on this. Suggested I call a premium rate number to get help. I told them to disconnect me. I'm now looking for some sort of alternative, and hence stumbled upon this page.
Legally I'm not sure that they can sell us a router, then wash their hands of its non performance. Only 1 hour on the phone in total though!