I used to try repeatedly power on/off for dozens of time, the eth in u-boot still works fine (and I suppose it would be OK after the coming Linux too..), could you confirm how do you boot your Linux? is it a tftp booting? what I want to know by asking this is if your failure happens in the u-boot too, or it happens only in the Linux.
One more clue is, we recently has a big change in the ethernet driver, and you can get the updated code from our git trunk on the sourceforge, the performance is enhanced, and we would recommend to you check your stability issue on the newer version too.