I had exactly the same prob about a month ago, I used to use DD-WRT firmware for my router and everything was fine, I updated to a newer DD-WRT and then got exactly that- average ping is always a constant 10-40, and after I updated I got the 10-40 but every 20-30 secs it would spike up to 200-300 for about 20-30 more secs then settle back down. Went back to original Linksys firmware and seems to be ok but I still sometimes get it, I know you say you haven't changed anything but you could try re-install firmware see if it changes anything, update PB, and check to see if your ISP has changed in any way- mine did without notice, I only get a 2 meg connection (which is fine) but now after midnight they cut it down by half on the upload and download so before 12 I get 2 meg, 250kb upload, after 12 I get 1 meg, 125 upload, which causes ping spikes too, I think it's a fair usage thing, which isn't really fair because I pay for the 2 meg so I should get it. If none of those maybe try a virus scan to see if any viruses are nicking connection speed, or any programs that could be using connection speed like Win update etc, or try changing the PB_sleep setting to a high number so it doesn't check it as much (not sure if that changes connection or CPU usage) that's all I can think of anyway