mysteriously changing mac address

[Nick Schmalenberger <nick@schmalenberger.us>]

Hi,
I have a g3 imac running a stock 2.6.20-1-powerpc kernel, and it has
been up for 20 days. Today I noticed that it's mac address had changed
to 00:01:aa:00:04:00 from the apple address it has always been ( dmesg |
grep BMAC tells me: eth0: BMAC+ at 00:05:02:b7:63:d8 ). When I did
ifconfig eth0 hw ether 00:05:02:b7:63:d8 to change it back, it became
00:01:00:05:02:B7. The first 32 bits of my real mac address are stuck
onto the end of the field! Has anybody ever seen anything like this
before? The next thing I am going to try is what address it uses if I
reboot. Thanks for all help.
Nick Schmalenberger