'Concentrator not reachable'

Hi.I've had this problem every few weeks or so, typically lasting 10 minutes. My Internet connection will go down and any attempts to reconnect on the 192.168.1.254 router homepage will give an error message of 'Concentrator not reachable'. It eventually reconnects, but it's happened 3 times in a row today and I'm wondering what the problem is? Thanks.