I went ahead and put the new code on the old board, but it worked fine, so I knew it had to be something to do with the differences of the boards. I started a new Arduino project file and kept slowly adding things in with it working fine until I got to the SPI stuff. Looking closer at the Arduino documentation revealed that the boards did not use the same pins. However, the 6 pin ICSP headers had the SPI pins on them and were consistent between boards. I went ahead and made some modifications to my shield and wire harness so that it was able to plug into the ICSP header rather than be wired to the board. I went ahead and tested it and the SPI code was working again. Unfortunately, there are now additional things to plug in between the 2 arduino boards, so I will most likely redesign my shield eventually and have it plug directly into the ICSP header in the new design. I'll also be able to take advantage of all of the extra pins that way, but before I get that far, I'll build some more sensors. First though, I'm going to get the tablet working with the robot and go from there. At least this is forcing me to review all of my old code, which is very helpful.