I'm the guy that Martin (paulnet@ipa.net) listed on the Quattro list 
with the brake problem over in Eureka Springs, AR this last weekend.  I 
thought that I'd pass along how the problem turned out.  I appreciate all 
the advise that everyone passed along to Martin who in turn forwarded to me via 
several pay phone calls. 
 
The problem indeed was the Master 
Cylinder.  I was able to get one through a NAPA store in Branson, MO the 
day after it was ordered through the store.  The only ill effects that the 
car seemed to have suffered was one warped rotor which has been turned and 
re-installed on the vehicle (I turned both of the front rotors).  The car 
now is back to its pre-vacation condition.  As a side note, when 
re-installing the MC I flushed the brake and clutch systems of the old 
fluid.  I replaced the fluid with DOT-4 following everyone's 
recommendation.
 
Again, I appreciate everyone's willingness to 
help a stranger in need.  Thanks!