ProgRock Serial - flickering led


Have my ProgRock connected to my arduino UNO, sketched as per the ProgRock Operations manual, switch 2 properly set on the ProgRock.  Boot up the arduino, power on the ProgRock, and voila, 4 flashes & firmware info appears in the monitor window.

One thing, though: with power to the ProgRock off, when I boot up (or reset) the arduino, the led on ProgRock flashes once brightly, then flickers constantly but dimly.  If I, then, apply power to the ProgRock, I get the appropriate 4 flashes, followed by firmware info.  If I switch off power to the ProgRock, led goes back to flashing dimly.  Power to ProgRock on again, gets the appropriate response again.

Anyone know what's going on?  Does it represent a danger to arduino or ProgRock?

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