Connection dropping each night - Cisco 857 Router

A few weeks ago we had an electrical storm which took out the router I was using at the time.. a Cisco 837 ADSL router. I had the Cisco 837 for over a year and in that time I never had a problem with my connection, it was always rock solid.

However the replacement Cisco 857 ADSL router is causing me major problems. I have set it up exactly the same as the last router (with No-Nat setup as I get 16 IP addresses from my ISP, Enta). At some point in the early hours of the morning, every night, the connection seems to drop off and I can no longer ping the router's IP address. To get back online I have to turn off the router completely and turn it back on again. I know not being able to ping the routers address would appear to be a problem with the router but the router connects using the virtual dialer interface and so if the interface isn't up, I can't ping the routers IP address.

Once I have rebooted the router it is then fine until the next night and I experience the same problem. It is a big problem for me now as I host my own websites and mail server and the downtime is very inconvenient!

Could anybody drop me any clues as to what the problem could possibly be?

Much appreciated. Thanks.

Could be a software problem... can you try a later version of the IOS? Firmware updates are also available on Cisco's ftp site.