Wiring Problems CAT5

I have a client who had his home wired with network(CAT5) and speaker wire all through out the house. I went over to hook up a wireless access point utilizing the CAT5 wiring and could not get a connection. Found the wiring was done wrong re-punched the wires tested out the wires and all pairs test clean straight through. When I hooked up the network and tested the wire using my laptop I get signal for a split second and then it drops of and Windows XP Pro says Network cable disconnected. Is there anything that could be interfering with the signal? Like power lines or the speaker wire? I am at loss since all of the pins are terminated correctly?