I'd vote for the spoke tension too. My LBS replaced the OEM wheel (Bontrager AT550) with a 'stronger wheel', because I was breaking a spoke every two weeks (in a brand new bike). Ok, I am 265 lbs, but I get off the saddle to cross an extension cord and still break spokes?

The new (rear) wheel came the day after I received the Park Tools Tension Meter. First pass showed 86 kg on the Drive Side and below the table readings for the non DS. LBS insisted that that is how the factory tuned it... 100 km later, I took the bike in and they adjusted the tension to 105 kg/71 kg, which is on the low side I think, but I am not sure how much force the rims can take.

Most of the 'factory tuned' bikes in the LBS seem to be tuned at the same or lower tensions, even the low spoke count wheels...