I have been experiencing this problem for the last week or two. TtHE MODEM IS ONLY 2 MONTHS OLD AND WORKED FINE FOR THE FIRST MONTH. They sent a guy to the house and he said the issue was with the main office. That was Tuesday, since they couldn't come on veteran's day. As of yesterday, I have no DSL connectivity at all.
Before yesterday, the issue was the same as yours. i would have to reset the DNS or reboot the gateway contantly. Now I haven't had internet for 24 hours and they are saying it could be another 24. Guarentee they aren't a moment late with their bill though.
-Good luck and keep me posted on progress. Is it still happeneing?