I have an Arduino Uno that's been working well until now. When I connect it to my MacBook Pro via the USB cable, the green power light turns on, but the L, Rx, and Tx LEDS don't light up at all.
This has happened with two other Arduino Unos of mine; after a few weeks of functioning reliably, my laptop suddenly can't upload programs, and they can't reset.
Any ideas as to what might be going wrong?
Something is killing the USB/Serial chip?
Does the Loopback Test work? (in the Installation Troubleshooting forum)
Rx & Tx only turn on when data is coming from the PC (Rx) or going to the PC (Tx)
L only turns on when D13/SCK is high.
Any ideas as to what might be going wrong?
One possibility is static discharge. You don't always need to see a spark to damage a component. You might want to use a [u]grounded wriststrap[/u] when handling electronic parts and circuit boards.
Where I work, we are required to wear a wrist strap or foot-strap (the floors are conductive for the foot-straps).
Is this a clone or actual arduino? What circuits have you been using?
Have you tried to use these on any other machines at all? a PC even? or another MAC of some kind?
Hi,
I don't know much about MACs but like Vindows you should be able to see, via some sort of control panel, what all your vitual COM ports are.
Look there to see if your Arduino appears and disappears as you plug and unplug it.
Tom.... 
Shouldn't the built in LED blink twice at startup if the bootloader is working?