welcome to the forums. I vaguely recall similar error messages many moons ago, but I'm sure we'll see you right.
You don't say which version of Firefly you have installed. Permit me to suggest that you go grab the 'nightly' version 1586 from
which is 18 months old now & very stable, in spite of it being a 'nightly' release. It contains huge improvements over earlier versions and the official release available via Roku.
Be sure to run the stop & uninstall scripts before reinstalling and you can physically check that you have trashed everything by checking for the Preference Pane in System Prefs, and also confirming that there is no Firefly folder/files in /yourusername/Library/Application Support.
Empty the trash then double click the Preference Pane icon to install 1586. As you have previously done, shorten the name, point Firefly to the /iTunes/ folder (no further than that) and hit the start button. As you may have read Firefly for Mac often hangs on initial startup so let it run a while then stop & restart the server. It should then show up as a shared server in iTunes and of course on your Roku device.
Holler if you need more help.
G5, OS X 10.5.8, 3 x M1000, iTunes 10.4, slimserver 6.2.1/alienbbc (now redundant), firefly svn 1586, uNSLUng 6.8