It could be that the cables running to your house from your cable box outside could be frayed, beat up, or exposed due to weather and wear/tear. The blinking lights usually mean your modem is trying to establish a link with your ISP but can't. So if it's not a connection in your house, it could be connections outside, or it could be a bad cable itself. Cross-check with your TV - although they run on different frequencies, if you see less clear signal in your TV, you know that it's a problem outside.