I am able to launch Mach3 (in Vista) and Mach3 discovers and initializes G100.
It seems some or all functionality is available... Do I need to "Run Firmware" from within G-REX Download Manager web page to use G100 with Mach3?

Mach3 ver: R2.00.065
Plugin ver: 2.00.064
G-Rex Autoboot: 0 (firmware not being auto-loaded)

Hi, you definitely need to run the firmware. That's how the plugin will communicate with the GRex.
Unless I'm missing something here, setting the autoboot to zero would launch the firmware without waiting (wait zero seconds).
The challenge could be to get back into GRex with the web interface since the firmware will already be running.

Thanks for responding!

I couldn't get the problem to repro (reproduce), so I think it was just me and that the G100 was in "Run" mode. Oh well. 

Here's the G100 Firmware Manual text on "Autoboot Time"

Auto Boot Time
If you enter a value above 3 (seconds) in this field, then the G-REX will automatically start the DLP
firmware after this amount of time, after it is powered up. Before this time limit expires, if you connect to
the G-REX with a web browser then the timeout will be cancelled. A minimum timeout is required to give
you time to connect in case something goes wrong with the DLP firmware.
If you enter a value of 0 for the timeout, then the G-REX will wait indefinitely in the download manager.
In this case, you will need to start a web browser session to the G-REX, then press the "Run Firmware"
button in order to start the DLP firmware.
It is recommended that you set this to 0 when trying out new firmware. When happy with it, set the value
to 3 or more so that the new firmware starts automatically.

-Cheers!