some folk (me included) have had problems with compressor.
namely the dreaded "connot conect to background process" warning.
the solution was to UN-install FCP and compressor, and re-install them.
FCP first, then compressor.
what a drag!
after that i helped a freind install, and rather than the "easy install" we did a custom one, and unchecked compressor.
after everything else had gone in, we installed compressor.
it worked fine first time.
nick