I'm seeing the same problem. I'm running 10.6.7 and at first QS was running fine.
It hung recently and after killing it I can't get it to restart. I've removed all of the config files, including cache files, still no joy. I do see several message in the console like the following: 3/25/11 10:26:33 AM Quicksilver[93148] Prevented load of unidentified action from bundle Core Support.qsplugin because the action's featureLevel (set from its Info.plist) is higher than NSApp's current featureLevel. This is not neccessarily an error. Sometimes this mechanism is used to prevent unstable actions from loading. On launch the 'QS' icon spins on to the screen and does not disappear like normal.
