I am unable to program 28377S on a custom board.

I am using an XDS100 JTAG adapter and Code Composer Studio 6.

The following error is displayed:

C28xx_CPU1: GEL Output:
Memory Map Initialization Complete
C28xx_CPU1: Error: (Error -1044 @ 0x0) The debug probe reported an error. Confirm debug probe configuration and connections, reset the debug probe, and retry the operation. (Emulation package 6.0.628.1)
C28xx_CPU1: Unable to determine target status after 20 attempts
C28xx_CPU1: Failed to remove the debug state from the target before disconnecting.  There may still be breakpoint op-codes embedded in program memory.  It is recommended that you reset the emulator before you connect and reload your program before you continue debugging

I've verified +3.3V and +1.2V supply voltages to the chip, and the XRS pin..

Any suggestions where to look next?