I had a Linksys router - the same model I think - a while ago and, periodically, it just stopped sharing anything. Resolved by pulling the power plug for 10 secs and then powering it up again after which it would work well for another couple of weeks or so. Firmware upgrade made no difference. Didn't seem to be particularly warm so I'm inclined to think it was just one of those hardware glitches/bugs that happen.
Maybe not what you want to hear but the reason I no longer use it is because the wireless bit gave up the ghost (wired connections were fine but no wireless signal detected by any devices).
Makes a good door stop though......