I've never had this happen before and have no idea how to solve the problem.
I'll contact CW support later and see if they can help.
I had the exact same issues on Wednesday, got home and my DSL was disconnected. I contacted support to double check my logon details and the correct details were entered on the router, the support agent then forced an authentication again from his side and my connection worked again.
And yes I did reboot the router and checked the credentials several times before contacting support.