I had a previous issue with the Microcell. it kept losing the 3G signal and that light would go out. This was resolved when I got a new modem.
NOW: all of the lights on the Microcell remain lit, but, after 2 weeks of working fine, the Microcell is not showing up on any of our iphone 4 units. I have unplugged and replugged the unit and turned the phones off and on.