That error has been exclusively showing up on 1117 firmware machines. The downgrade to the april firmware always fixes it for me.
Thanks! I should have guessed, that did the trick for about 90-95% of them. It seems on a select few the issue still persists, although the kernel log hangs on "Start bmminer ..." instead of giving endless output.
Also, what is your preferred method of flashing firmware when you encounter the code 413 - Request Entity Too Large? Is there any other method besides using a microSD card, and how exactly do you put the firmware on the microSD? Do you extract the files first? And what format, is FAT32 sufficient?