First, do you have security enabled on your wifi? and does it have a key?
Second, turn all your items off that are using WiFi or have ever connected to your WiFi network. (ie, Xbox, PS3, Phones, Pda's, DVR Receivers, computers, etc)
Third, Reset your modem and router.
Fourth, Try to connect back to the network with the mac you used above, see if you can connect. You should be able to by now, and connect each device back to the network one by one. For some reason it looks like a device either was connected and timed out or 2 devices connected at the same time with the same IP address and only 1 is allowed to be on per IP.
Let me know if this works. PM me for more help.