Aha - you're right!
$ echo $PYTHONPATH
/usr/lib/python2.7/site-packages/mpich2
So after I set the PYTHONPATH to the one in /usr/local/lib... specified by Marcus, ***gnuradio-companion started up for the first time! ***
And you are correct - I did in fact have an old gnuradio RPM hanging around out there (it was a dependency of some other AX.25 stuff I was using so I thought I could get away with "overwriting it" with the compiled version of gnuradio, but I was wrong.).
Here's what I've learned from this experience
#1 - It is possible to run gnuradio + grc on Fedora 14
#2 - Install all development packages required to make the build process successful (if unsuccesful then it's due to missing dependency package)
#3 - Install gnuradio + grc from git source (as specified on gnuradio wiki page "BuildGuide".
#4 - Make sure that
PYTHONPATH=/usr/local/lib/
python2.7/site-packages. If not, then there is another instance of something (gnuradio?) conflicting with the newly built one.
#5 - The gnuradio and grc which currently ship with Fedora 14 are outdated, and seem to be broken/misconfigured (they don't work out of hte box).