I'm having the same issue on a handful of em357's. In my case, shorting PA5 to ground during em3xx_load does not seem to have any effect. Can you expand on the issue?
It's a general failure during JTAG/SerialWire communication, so it's hard to "expand" on what could be the problem. If you want to discuss your particular failure in more detail, please raise a new discussion thread in the Wireless forum so we don't hijack this KBA.
I'm using the ISA3 to program a Telegesis ETRX3USB Dongle (em357 chip) and am running into this error, any suggestions on how to get around this error?
Wrong AHB ID
If getting this error message when trying to flash a Telegesis dongle: