[stevedusa]

If you have an Intel Mac, what I suggest you to do, safely is use Boot Camp. After all no matter how much it can emulates (or runs natively) Windows in a OS X environment, the USB pass-thru the OS X kernel to the virtual machine can cause issues.

Keep in mind that when the phone goes into Bootloader mode, it became a different device. Translation: USB connection drops, VM doesn't see it and you need manual reconnection to the VM. Also, not all VM support certain modes where USB is emulated as serial or plain USB.

What you CAN do is rename the ROM file according to the phone and put it in the root of your SD card, boot into the bootloader mode and flash from the SD card. That way you don't have to worry about having the flashing procedure takes a dump and brick your $700 phone.

For those who still has a PowerPC-Mac, well... find a PC, or try the flash from SD card method.