I know this is an old thread but i am having the exact same problem the OP had. But it takes about 4 or 5 days for my 10MB speeds to drop down to about 3MB. My last reboot of my WRT110 was 3 days ago and my speed is now down to about 8MB, will be down to about 3 or 4 in another couple days. It has been doing this since i got this from my older brother a year ago.
This desktop computer i am using is hardwired directly to the wireless router.
I called customer support and was told because the warranty was expired they could no longer provide free phone support. But if i wanted to order a new wireless router right then and there, by golly they could then give me free phone support. No thanks. I'm going elsewhere next time.
I looked up the firmware and had support confirm that there is no new firmware for this older wireless router. All i find on their website is version 1.0 firmware. I read where they had updated the firmware in the past but had problems with it so they must have just took them down.
Just wanting to know what i can do to mine to keep it from slowing down all the time. Will reflashing the original firmware make a difference?