8x8x8 Cube of RGB LED's

I have my Arduino set up with two 1 to 8 demultiplexers on six of the fourteen available pins. The output of these two demux's then go into four RS latches to keep power on the LED's. I have my Arduino cycle fast enough that it's barely noticeable when the LED's change or turn on (since I have to turn them all on separately). The RS latches have the reset on pins zero and one (where I've never had a problem hooking them up before). Although, there isn't a problem with any of the set up (it worked when I had only one set), the problem arises when I have all six of the outputs turn on and I read with my digital logic probe a HIGH and a LOW, at the same time, without a pulse. This isn't just on the outputs that are on, it happens all across the Arduino board. (Also, for power on the chips and LED's, I found that I had to use a 5v power supply.)

So, my question is: why do I get a HIGH and a LOW reading when the outputs are all on?

I have not tried to rip apart the circuit and start over yet, it took a while to get put together.

Schematic? Code?
The analog pins can also be used as digital IO, so 20 total.

Sorry, should have been more specific. The problem was solved by connecting the external power supply's positive lead to the VIN pin on the Arduino UNO.

How do you use the UNO's analogue inputs as outputs?

demandingiowa: Sorry, should have been more specific. The problem was solved by connecting the external power supply's positive lead to the VIN pin on the Arduino UNO.

How was the Uno powered before you did that, since it was 'somewhat' working? The reason I ask is that multiple voltage sources to a single item are usually not a good idea. With that, the 'stronger' (higher V) source will be pushing power into the lower V source.

When two separate items fail to communicate properly the usual fix is to common the grounds at one point.

So, my question is: why do I get a HIGH and a LOW reading when the outputs are all on?

-Either- because it's -cleanly- cycling between high and low very quickly, -or- it's at an 'in between' voltage that the probe can't decide which to display. With enough LEDs you might be experiencing voltage drop when 'a bunch' of them turn on all at once.

@demandingiowa : A0 to A5 can be addressed as 14 to 19 for digital use.