Arduino can't find my custom library: fatal error, Motor.h not found etc
I wanted to vote for the answer from trpropst, but I don't seem to be authorised to do so. 

I had the same problem as Caleb. It turned out that the problem was that the user library directory /Arduino/libraries/ contained a library with a missing ".h" file. The Arduino IDE stopped loading the user libraries when it reached the library with the missing ".h" file.

i.e. 

the folder "/Arduino/libraries/libraryA" existed

the file "/Arduino/libraries/libraryA/libraryA.h" existed

but the file "/Arduino/libraries/libraryA/libraryA.h" had an include

"#include &lt;libraryB&gt;" for which the folder "/Arduino/libraries/libraryB" existed but it did not contain a file "/Arduino/libraries/libraryB/libraryB.h" 

I was trying to compile a program using libraryC, but not using libraryA or libraryB. I guess the lesson is do not develop libraries using the production tool chain. 

edited to print &lt; and &gt; correctly