Urgent help needed - arduino power issue!!

I really hope someone can help with this - using my device to power the lighting on a festival stage in a few days!!

Ok so I have made a 'boarduino' from the designs on ladyada. I am using a TTL cable to upload to a 328 with UNO bootloader on it. It has been working perfectly for some time and now, for no reason I can think of, it only works properly when receiving power from my macbook pro. The device is not receiving an serial data over usb to work, just power. If I plug the same TTL cable into my other laptops, no joy. The DC jack on the boarduino now gives the weird behaviour also.

The 'weird behavior' is that some DMX fixtures are not recieiving the correct data.. whereas if the device is powered by my macbook pro, it is!! I am totally stumped.

What could differ between powering from my macbook pro and off anything else??

Any help pleeaase!!

It may be a problem that the Mac is the only device that delivers enough current. Do you know the current your circuit needs and how much each power source is delivering?

Are you using the 3.3v pin on the Atmel chip?

Thanks for the reply, I'm going into the two VCC pins on the atmega328 (pins 7 and 20).

The circuit has a 5v regulator for the DC jack. otherwise, it takes power straight from the TTL cable.

What is the rating of the supply using the DC jack?

Can you provide more information about your setup?

The supply is a 9V / 12V switchable 600mA DC mains adapter. The board is exactly the same as this one:

Maybe it has something to do with the DMX requirements... Everything about the circuit works, apart from the DMX fixtures, and it's only then power supply that affects it.

This is quite odd then. When you say no joy with other laptops - do you mean boarduino isn't powered?

Could you try a USB hub or another USB power source?