Help Screen flashing?

[pappy53]

I have noticed that when I am charging my wi-fi Xoom at night that the screen flashes a "glow" about every 5 seconds. What is this, and is it normal. BTW, it can only be seen in a dark room.

 

[marctronixx]

i use the xoom as a deck clock when its in the HD dock, so the screen is on but the brightness is greatly muted so just the clock shows.

the room is usually fairly dark, save the light from the xoom's screen.

ive not seen the xoom do this. ive had it since launch day. stock rom not rooted.