[mythtv] how is the aspect ratio set in mythtv?

[Timothy Flechtner]

hello everyone,
  i have a redhat fedora core 3 box, which i recently updated (via yum) 
to the latest and greatest versions of everything.  this, in retrospect 
was maybe not so bright an idea, as now myth believes it is displaying 
things at 4:3 when in reality, it is not.  the display takes all of my 
widescreen tv now (when in 4:3 mode).  prior to my updating all 
packages, it did not (4:3 actually was 4:3).  mythtv does this when 
showing live tv, playing things recorded from tv (which were recorded 
prior to the update, and showed in 4:3 prior to the update), and when 
playing videos.  i use xine for videos, and when i run xine outside of 
myth, it correctly shows things in 4:3 when set to do so.
  i realize my descrition is pretty vague, but can anyone reccomend 
things for me to look into?

thanks!!
-tim