sent an complaint email to ur ISP, they might know what the problem is, also, check your wiring... an improperly connected cable CAN interupt ur internet connection.
also, there may be a fault in the router itself. if it's provided by ur ISP, ask for a new one
i have same problem, random DC's, i sent an email to my ISP, and i got a reply saying it was probably my adaptor, so they sent a new one, this didnt solve the problem, so they sent a brand new router, alfter i sent them a 2nd mail..
worth a shot