I just got stung by this too.
Turns out I have an earlier version of the PCA10000 board. Check your board to see if you have V1.0 like I do. If so, this fix is easy… once you know anyway.
Go to Includes/boards/pca10000.h. There is an #if /#else construct for selecting between board versions. Change to #if 0 for V1.0 and away you go.
So I made a new version of pca10000.h changing the one critical character from a ‘1’ to a ‘0’!