Some routers seem to be more tolerant on noise than others. For instance the BT Business Hubs (branded as 2-Wire) are awful
What are you using at present? Also who is your service provider? BT or someone else?
There are tricks you can play on the router
Changing the MTU is one. BT used to say that a setting of 1458 was best in the old days of ADSL, but that became irrelevant with ADSL 2 / ADSL+
However it could be worth a try on a noisy line
Set the MTU on the router to 1458 and see what happens. You could try pushing it even lower to see what happens, but don't drop below 1400
There used to be a BT script file available for download which would also set the MTU of the network port of the PC to 1458 (so that all balanced) but I've not seen it for a while. I no longer have a copy (it dated from Win98 days...)