I tried DEFINE SHIFT_PAUSEUS 100. Still no output.

I used a logic probe to verify activity on the serial and clock pins. I can watch the CS pin go low. Activity on the LCD screen verifies the program is running. The PIC seems to be doing what it's supposed to. I changed the Shiftout command to:

Shiftout alldata,CLK,1,[%1111111111111111\16]' Shift out the 16-bit word

This should output 5V on output B.
Still no output.

The differences between this chip and the LTC1257 are: Configuration bits, hardware and program shutdowns, LDAC signal. I think I've addressed all of these. Using essentially the same code as below, just without configuration bits, I verified the PIC16F877 I'm using will drive the LTC1257. I've exhausted all my ideas for now. Any thoughts at all are welcome.