I am running a fully patched version of Red Hat 7.2.  (As of Apr 25, 02.) 
Adding the first printer works fine. Additional printers (print queues) don't
work. If I would run
printconf or printconf-gui the printer would show up there, but attempting to
print test pages would fail. After further investigation, I found that it was
not writing anything to /etc/printcap or creating the queue directory in
/var/spool/lpd.

Simply having mpage installed does _not_ fix this problem.I have the latest
updates to 7.2 and mpage installed and still have almost the same problem.

If you, as root, create a single lpr print queue, stop and start printconf-gui,
(close the window and re-open it), create a jetdirect print queue, restart
printconf-gui (I think), delete the jetdirect queue, restart printconf, and try to
create another lpr print queue, the last print queue does not make it into
/etc/printconf or /var/spool/lpd.  It does show up in the gui through.  There
may have been some other edits of the jetdirect queue in there, maybe attempting
to change it into an lpr queue.

At this point a new queue never makes it into printcap.

Running 'printconf-backend --force-rebuild' as root updates printcap and makes
the queue directory.