The university I attend scans student and faculty machines with an agent (Bradford) to ensure they comply with policy (i.e. AV is installed and up-to date, and the OS is patched). The system's MAC address is then tied to a user's domain account. Sometime last week, the campus network started claiming that my laptop was unregistered after a reboot.
I contacted a network admin, who discovered that five different MAC addresses had been associated with my laptop's WNIC. Upon further investigation, I discovered that somehow, the last two hex digits of the WNIC MAC that is reported to Windows 7 has started to change after a reboot of the system. I don't use any spoofing software.
Could this be caused by faulty hardware? The MAC prefix (00E04C) does correspond the correct OEM (Realtek). The WNIC is a RTL8723AE. My next step is to see if the same thing occurs when booted to a Linux distro.