PWM frequency library

Hi!!
I just want to say, thanks for the library!!!, it seems to be very helpful, because, as you said, you did found a necessity, and well, you are now giving us a solution... Well, then, I'm an Arduino begginer ^_^, and I'm developing some project that involves the use of Ardu...and also the PWM management, thus, its frequency.
I did download your library, but, when I compile the first example, in the IDE message area says:
"PWM_lib_example.cpp: In function ‘void setup()’:
PWM_lib_example:23: error: ‘InitTimersSafe’ was not declared in this scope
PWM_lib_example:26: error: ‘SetPinFrequencySafe’ was not declared in this scope
PWM_lib_example.cpp: In function ‘void loop()’:
PWM_lib_example:38: error: ‘pwmWrite’ was not declared in this scope"

Also I was reading some comments, that it actually works perfectly =(...what you think could be the problem?? It seems like the IDE does not detect the #include <PWM.h>...
Thanks!!