[waldojim]

Ok, here is what I have, work with me a moment, I don't do this everyday.
You are working with LEDs that have a 10.6 Ohm resistance.
Wonderful proofing calculator.
You have a 56 ohm resister in series with each LED, bringing a single chain to 66.6Ohm resistance.

Using the Value over Number Formula, running 12 LED sets in parallel brings you to 5.5 Ohms total resistance.

Now, I make absolutely no claims on being a genius, so I will throw out my guess and let it go from there, but it seems to me, that 5.5 ohms is quite low. Low enough even, that the power supply may be sensing a short. Try reducing your parallel LED count to between 2 and 4 units. If the unit works correctly here, then I fully recommend using a "dumb" power source. IE a battery.

[LiveBrianD]

As I recall, I had tried using only two LEDs at once, and it worked a lot better. (though even there, I didn't quite have double the current of one LED) I'll try a battery once I get around to it though.

[LiveBrianD]

Since I've got two weeks of break coming up, I'll have some time to mess with this.

I have a 12V power adapter (from an old phone, 200mA) lying around, so I figure I'll try that. If each LED uses 3.5V, 25mA, 3 of them in series with a 56ohm resistor should be about right. (and then I have fewer parallel circuits)

[LiveBrianD]

I just figured it out - the USB CABLE was causing the problem. I'd taken that out of a LED USB thing from CVS, and I wonder if there's a resistor built into it by design (I didn't see any on the actual LED in that, and was wondering how they were feeding 5V into an LED without blowing it out...). I switched cables, and now it works perfectly.