after just dealing with a very annoying problem (be careful to never have a trailing whitespace in your BOARD definition in your project's Makefile...), I've extend the Troubleshooting section in the Wiki a bit. Please feel free to document whenever you encounter a generic problem (and have found a solution) here:

In general: whatever you think is important for a better understanding of using and developing for RIOT: please add it to the Wiki!

Cheers, Oleg