No serial connection to xM board

Hi folks,

just trying to get some more information on ways to possibly debug a
presumed hardware defect of my shiny new xM board while waiting for
the store to get back to me about an RMA.

The symptoms I'm seeing are the following:
Serial on the board seems to be dead. Using a serial2usb connector, I
don't get any output whatsoever from the board. Looping back the RX/TX
pins on the serial adapter gives me an echo in minicom, so that should
be working.

I can boot the board into the validation image that came with it and
ssh in (if I play some dhcp games). If I loop back RX/TX on the board,
I don't get any echo on ttyS2 on microcom.

I folded and bought a voltmeter, and there seems to be no voltage
difference between TX and GND on the serial connector. After a tip on
IRC, I also measured pins 3 and 7 of the U9 chip right above the
serial connector vs. ground, which gave me a voltage of +-2.3 V as far
as I understood, those pins handle the maximum/minimum voltage on the
serial, and looking at the specs that voltage should be between +-
3-15 V.

This does not explain why I'm not seeing any voltage at all on the
serial, so I'm not sure if that's relevant.

Any other ideas on how I could debug this? I'm currently at a
conference, so I don't have much equipment to play with.