I missed step 5 in this article from CNET - and it totally solved the problem for me (I didn't have to do any steps after #5, but I'm not sure if it's necessary for you).
by Conduit_Support January 10, 2011 2:57 AM PST
Two ways to completely remove community toolbar powered by Conduit:
One: Run /Applications/Toolbars/<Toolbar name>/Uninstall.app
In case the application fails you need to delete the followings:
Open the Finder application:
1. Browse to: Machintosh HD -> Library -> Application Support -> Conduit -> Plugins
2. Remove Plugins directory.
3. Browse to: Machintosh HD -> Library -> InputManagers - > CTLoader
4. Remove CTLoader directory.
5. Browse to: Machintosh HD -> Library -> LaunchAgents -> com.conduit.loader.agent.plist
6 .Remove com.conduit.loader.agent.plist file
7. Browse to: Applications -> Toolbars
8 .Remove Toolbars directory
9. Browse to: Machintosh HD -> Library -> ScriptingAdditions -> ct_scripting.osax
10 .Remove ct_scripting.osax directory
Read more: http://reviews.cnet.com/8301-13727_7-20027867-263.html#ixzz1B4UMveEY
Once upon a time I had installed some toolbar and then uninstalled it, but every time I launched Safari I got a message that Community Toolbar was not compatible with it. But that was the least of my problems. I was never able to download Safari extensions (or even see the download buttons for that matter). It was as if I was still using Safari 4. This has been going on for years. I've talked to Apple, I've searched Apple Discussions (although not lately, obviously), I've posted on other forums, all to no avail. I am so happy to finally get extensions working. I did find on thing on my mac that I don't think has been mentioned thus far: CTConduitBundle that was in Library/Application Support/Plugins.
Thanks for all your help!
Ok, with the help of a friendly sos apple person I was able to uninstall the morphster toolbar from my firefox application. I also had to reset my home page (which morphster had reset.)
THIS IS THE BEST WAY TO DO THIS! THANKS SO MUCH
1. Open Firefox.
2. Under Firefox open Preferences.
3. Under the General tab reset your home page.
4. Under the General tab click on "manage add-ons."
5. Choose uninstall for both the conduit plug-in and the community plug-in.
6. Quit and restart Firefox.
Hope this helps anyone who comes after me. Avoid Morphster's home page under all circumstances!
I found the problem started when I downloaded something called 'torrapp'.
This may be a rename of the same problem caused by 'Morphster'. The word 'toolbar' was not present.
I would avoid downloading 'torrapp' since it seems to cause the same problem with the 'community toolbar'
Thanks to everyone for the energy spent in trying to solve this problem.