I had discovered a bug in the version of u-boot (1.2.2) that shipped with my 9260 board, and wonder is anyone else has seen it…
Try saving a ethernet mac address to u-boot’s environment, and then try to make any other changes…
setenv ethaddr 00:00:01:23:45:67
saveenv
setenv ethaddr 01:23:45:67:89:ab
saveenv
I have a version of the latest u-boot (1.3.4) working on my board, that I just have a couple of other things to clean up. If you wish to try it, let me know.