Skype is on similar style like phone cable, so make sure it's closed. It can be problem, or some similar program. Make sure your router isn't too hot, and his temperature is good. Maybe some virus can be problem between your pc and inet. Please specify your router used. Try run msconfig and check what progams or stuff is running on startup, there can be sth new sitting on your connection? Check your HDD or SSD storage left, if u are on few GB it can be prob too sometimes.