For what it's worth, yesterday I upgraded my main machine to SL4.2 (from
3.0.4).  I enabled dag and dries, and yum update produced an conflict
and refused to update anything.  (Sorry, I neglected to note the error.
Something to do with Java, I believe.)

I disabled dag and dries, and the next update worked fine.

-- 
Richard S Holmes <[log in to unmask]>
Syracuse University physics department