If you have a problem with Quicksilver, you're probably not the first. Try searching the Google Groups for your issue (Search field, top right).
You may also want to check through the most commonly asked questions in the FAQ.
There are several known applications which interfere with Quicksilver, there is a list of them on the Known Bad Applications page.
You may also like to search @LoveQuicksilver's Twitter timeline for past tweets.
Send a tweet to @LoveQuicksilver for help if all else fails.