i do not understand that "bootm" command.
why are you booting from ram instead of flashing?
is that a ramdisk (initramfs) image??
Sorry I should have been more clear. The tftpboot/boom command sequence is for booting an initramfs image, which I was not using originally as I misunderstood the use of bootm. So ignore my use of bootm as it was wrong.
I have been running trunk r39422 on v1.7 WDR 4300 for a few days without a problem. I flashed the image using the tftpboot/erase/cp.b sequence of steps as outlined here. I never tried using the factory firmware upgrade webpage.