There are a number of errors that fall under this category.  But they all have the following common elements:

1. Getting an error when attempting to use em3xx_load
2. Part of the error message says 'Target not recognized as an Ember device.'   This problem often arises if the EM35x has been interrupted during a programming/erasing operation via the ISA3.  Examples of interruptions would include pulling the power or pulling on the reset line while the chip is programming/erasing.  It is recommended that other chips interfacing to the EM35x be locked down during programming operations.

If you find your EM35x in this state, there is a general recovery mechanism.  You will need to short the nBOOTMODE pin (PA5) to ground, execute an em3xx_load command (such as '--erase'), then release the PA5 pin.  After this procedure, the EM35x part should function as normal.