missing "CCCC..." on serial port of AM335x EVM on power up, is it dead?

normally, upon power up, the AM335 General Purpose EVM would display "CCCCC..." for a brief period before it moved on to regular uBoot messages etc.  Well, it no longer boots, nor do I get any activity at all over the serial port.  It clearly isn't booting.

So far we get power at many test points around the processor, though current is only drawn by the clock and ddr (as determined by the test pin pairs across the shunts).

We had external connections to level shifters on the spi0 pins when the failure occurred.

Beyond half-stepping our way through the schematic, does anyone have any troubleshooting tips for this situation?  Any suggestion (or, consolation) would be appreciated.