This is, believe or not, NOT quicksilver's bug. Not really. Snow Leopard changed the nature of Services pretty seriously. The Service's plugin for Quicksilver was written for Tiger. It's not a bug, it's in need of at least a partial update.
However, I was going to take a look and see if Skype is applescriptable for you. And realized its very applescriptable, and wrote a Quicksilver action to send phone numbers to Skype to make a call. You can download it here: http://tr.im/D4J6 Install it to: ~/Library/Application Support/Quicksilver/Actions Then restart QS. To use, grab a phone number from your address book (requires the address book plugin), or type in a phone number in QS text entry mode. Tab over and type till you see callSkype, hit enter. This should work. I've got it set to first strip out parenthesis, dashes, and spaces from the number so you don't need to worry about that formatting. Then it checks if the first character of the phone number is a "+" (skype needs phone numbers to be in the format "+CCC1234567890", where CCC is the country code. If you want to call outside the US you'll need to make sure you numbers are in that format. Inside the US they can be formatted for skype, but if they're not (if there's no "+" at the beginning) the script tacks on a "+1" for you. If you store your numbers as "1(222)333-4444", that's ok too. In the case of numbers not starting with "+", the script takes the last 10 digits of whatever you send it and adds the "+1". I'll post this in the main board as an action as well. But you can download it at the link above.
