Sorry it took me this long to reply. I am currently away from home and on an unreliable modem connection.
 
As far as your problem is concerned, I would suggest doing the following:
 
Untar the package and cd into the source dir
 
make distclean
 
cd rtmix/
 
check that all the *.moc* files are gone
 
cd ..
 
try ./configure
 
make
 
make install
 
If you again encounter any errors, please post them here and/or e-mail me and I will try to look at them more closely.
 
Your problem is most likely caused by the leftover .moc files whose structure might have changed between the 3.0 and 3.1 Qt versions (and this should be no problem since the .moc files are generated at compile-time), but the Qt source code should work just fine.
 
Alternately, download rpm's for your distribution. Planet CCRMA has them for RH distro, while Eastman's Turnkey and Thac's RPMS offer MDK rpms (URL's can be found in the news ticker on these forums or on the home page).
 
Hope this helps!
 
Ico