Sketches behaving differently when the SERIAL MONITOR is activie

lost_and_confused:
I really hope not.

Just hoping is not good enough. You need this:

http://www.arduino.cc/playground/Code/AvailableMemory

You need to comment out a few long strings in your code to run this code, if your code is already running out of SRAM. What you described is very much like SRAM is running out.