What a great answer. Makes so much sense. I have put a timer in to reboot about 2am. I am also trying to reduce the amount of traffic on this router (Linksys WRT310N). Unfortunately the router is also out of warranty. I will try and increase its coolling too. Both routers are on different networks too. Unfortunately they are both different routers. Appreciated your answers.
Sometimes Routers have a problem with storing too much information or getting too hot. One solution is to have the router do a scheduled reboot each day. This will clear the cache and keep it working for you.
If you find that you are having furhter problems it could likely be a defective router.
One thing i would suggest, is making sure both routers are on different networks (ie 192.168.1.* and 192.168.2.*) this will help some traffic and routing problems.
Another thing you can try hacked firmware for your device (the only one i have used is DD-WRT)
lastly, if they are the same router, then save the configs on each and swap them around to see if the issue persists.