Recently I purchased a Seeeduino Arch Pro to research mBed. However, during an attempt to load a new bin file, I had accidentally held the button while plugging in the USB Micro cable. This caused the board to come up as MBED BOOTLOADER and it refuses to boot outside of this bootloader mode. It almost seems as though holding this button erased the main flashing program. After many failed attempts with different USB ports and powered hubs, I attempted to load lpc11u35_lpc1768_if_mbed.bin while it was in this bootloader mode. This caused the board to reset after the write was complete, but still does not come up without the button being held.
Also, this is consistent behavior. I used a secondary board that I also purchased, attempting to figure out what had gone wrong. Once I placed this board into the bootloader mode as well, the secondary board also no longer functions.