[DouglasKC]

If you had your network setup to accept only connections from machines with you MAC address then it's doubtful they hacked into your system. If they got your MAC then they probably would have had gotten physcial access to your pc. Unless there is some program that dupes MAC addresses somehow.

[Marnoot]

It's fairly simple to obtain a MAC address by listening to latent network traffic with a network traffic analyzer, and it's not much harder for a hacker to spoof his/her MAC address to match yours in order to gain access. WEP is fairly insecure, consider changing to WPA encryption.

Greg