I use Quicksilver - a LOT.
When the 2.5.6 upgrade (from 2.5.4) failed, even my efforts to debug, were painful - most would have started with Quicksilver. :/
Anyway, after over an hour, here’s what finally worked for me:

• revert to v2.5.4
• AND: delete /Library/Caches/com.blacktree.Quicksilver/