Please add a note to the "noInterrupts()" reference page (http://arduino.cc/en/Reference/noInterrupts) to say that if you call this function, since Serial.print depends on interrupts to send serial data to the computer, it will cause your program to freeze if you call Serial.print or Serial.println after disabling interrupts!!!
-This would have been super useful info. to me, and it would have saved me several wasted hours debugging!
See here for where I got stumped: Solved: reading PWM signal: the "noInterrupts()" function crashes my code! - #5 by panther3001 - Programming Questions - Arduino Forum
--adding the above comment I suggest would be very useful both here: http://arduino.cc/en/Reference/noInterrupts AND here: http://arduino.cc/en/Serial/Print