Snow Leopard - Quicksilver b56a7 doesn't get activated on Dock icon click or hotkey

[zebbie]

I recently upgraded my Mac to Snow Leopard, and Quicksilver worked
without major problems (I only use it for basic app launching). Today,
I tried to upgrade to the latest version b56a7, but I can't get it to
activate, neither with hotkey nor by clicking the Dock icon. I
restored the old Quicksilver from Time Machine and it works again as
expected. What is wrong?