Few days ago I set up Buffalo WHR-600D. I was happy there is already factory version of DD-WRT (v24SP2-build 23392) so there was no need to flash it. It work perfectly, that is, till around 7pm to 10pm everyday. Around then download speed drops from 50/20 Mbps to less then 10/20Mbps. This happens on LAN and also WLAN. So far I reseted ISP modem, my Buffalo router, PC in all possible combinations and nothing happened. When I disconnected router and connected directly via ISP modem/router I got normal speed. After a 3-4 hours everything goes back to normal. I already did hard reset on router, I reinstalled original non DD-WRT firmware and then reinstalled back to DD-WRT. All the same. I did have some difficulties with connecting from desktop PC directly to ISP, which didn't occur with laptops, so I figured maybe it could be something wrong with my LAN card, but then again...well I guess there wouldn't be problems with speed loss on other computers. More and more I'm sure it must be router, maybe some weird setting. I already changed cables, so I'm sure it's not cable.