If you have access to an oscilloscope, take a look at the voltage coming off the regulator to see if it is steady and is at the voltage you are expecting.
You say that you have 5V coming off your regulator, right? How do you know this? Measurement with a multimeter, oscilloscope, or just faith that the regulator is doing what you think it is doing? What kind of regulator is it anyway? 7805?
I don't have an oscilloscope at the moment.
The ouput of VR 7805 is about 5V measured using a DMM