I searched up D-Link DSL-G604T disconnecting in google and I found a topic with my EXACT problem
http://www.geekzone.co.nz/forums.asp?ForumId=49&TopicId=10577
My line continiously cuts out, its incredibly frustrating and I have no clue what to do about it. I don't want to buy a new router because I'm scared the same thing is just going to happen cept I'm going to lose $200 in the process! Anyone got any ideas :(