I don't think so. But, I am not sure where to look?
Apple Menu -> About This Mac -> "More Info..." -> USB
(now modified to use a toggle switch to change the blink frequency via my wife's Vista laptop).
Was this toggle switch wired before you started having problems? How is it wired? Are you using pull-up or pull-down resistors?
I do see some stuff in system.log when I launch the Arduino program:
If the OS is not reporting the device when attached, it doesn't really matter what the Arduino IDE sees. The IDE just asks the OS for what serial ports are available.
Also, none of the usbmodem files are in the /dev/ listing (no usb or modem either):
Just to clarify, the Arduino will only appear in /dev/ when it is attached. Are you looking when it is attached?
Not sure what you mean by no other hardware attached. The Mega is 'empty'. Other than the push/pull switch I just added to pin 12/gnd/5v, it has nothing else attached.
The Mega doesn't come with a push/pull switch, so that would be considered "hardware that is attached." How is this switch connected?
It is common for OSX to disable power to a USB port (or a port a known offending device is attached) when a short is present from that device. So depending on these switches you've mentioned are setup, you might be causing the port to shut down. (Though, OSX is usually very good about giving a warning before doing so.) In some cases, I've had to do a power-cycle before I could use the device again. Keeping in mind, if you power cycle and the device is still drawing too much current, you are just repeating the same mistake.