Please help my internet keeps going off and on?

I have verizon dsl which seems to be working fine it is connected to a linskys wrt54g2 modem I have two computers hard wired to the modem one is running windows vista and the other is running xp and in the other room we use the wireless connection for a tivo box we also use the wireless connection for a workstation 600 all in one printer which we very seldom turn on. our problem after it gets dark or in the evening we start experiencing connectivity issues to the Internet will be ok all day and then in the evening on for a while then off for 10 min or less then back on for 10 min or less I have talked to both verizon and linskys but I still have a problem please help