Had this same problem on my DGL-4300 as well. My ping spikes whenever I watch movies or torrent, even if it uses 10% of my bandwidth. Eg: On speedtests I get 60mb. I could be torrenting at 1mb/s, which is around the highest it goes on this router and my ping will rise. Doesn't happen on my trendnet router which can torrent up to 5mb/s without experiencing any ping spikes, unfortunately that router doesn't have wifi.