I appologize in advance if this should be posted elswhere in the forum, or if the topic has been already addressed.  I did search the forum and the closest I came to a solution was something along the lines of checking to make sure the seal was good on the oven.  Anyway, here's what's going on.

I just moved to Mesquite, NV (elevation 1579 ft) from Laughlin, NV (elevation 535 ft) about three months ago.  

For the year that I lived in Laughlin, I baked a variation on a simple sourdough (N [1]orwich Sourdough) maybe two dozen times without issue.  I baked on a crappy little broken circular pizza stone that we inhereted from somewhere.

Once we moved to Mesquite, I invested in a large 15" x 20" Fibriment baking stone that is almost an inch thick... Furthermore, I have my old pizza stone pieces resting on the top rack of the oven for some extra thermal mass.  The oven is a brand-new Frigidair.

During a visit from my mother couple of months ago, I tried the Tartine Country Bread using a combo cooker (forming a good seal, and adding additional thermal mass).  What came out of the oven was an absolute embarrassement.  I could feel it as soon as I picked them up... it was like moving loaves with rocks hidden inside.  Dense, heavy... and worst of all wet.

I was at a complete loss as to what could have happened.  A week later I decide to bake my old sourdough right along side the Tartine country bread for the purpose of comparrison.  Both loaves came out dense and wet inside.

Now I was scared.  I went out and bought a hanging oven thermometer to verify temperatures, and over the next three weeks I tried everything.  I verified the ripeness of the starter, I double checked the gluten developement during kneading, ensured that the loaves had fully proofed before baking...  nothing.  And yeah, I checked the seal on the door of the brand-new oven.  Each time, they still came out wet.  This has become a nightmare.

This week, I am pulling my brand-new baking stone out of the oven altogether and baking on my old crappy pizza-stone, in order to almost ritualistically reproduce every condition that I used to have in place when my loaves came out beautifuly.  But I don't think it will fix whatever is going on.

I'm open to any ideas.

Thanks guys.