I had this problem as well. I upgraded to Mountain Lion, and LaunchBar kept getting stuck on indexing. I didn't have a Bootcamp partition, but I do have four external drives attached to my iMac. Excluding the four external drives from my Spotlight and restarting LaunchBar did the trick. As a side note, to exclude drives, go to the Spotlight preferences in System Preferences, click on the Privacy Tab, and drag the external drives into it.
↧