Is Quicksilver giving you an "Installation Failed" message?
Previous versions (namely ß61 and ß62) of Quicksilver had a serious bug that broke automatic updating. Please download the latest version manually. You should not see this problem again, and we are sorry for any inconvenience.
To find out what's new in the latest version of Quicksilver, see the changelog.
A full list of previous downloads can be found on the GitHub downloads page.