Topic: Pingbacks got you stumped?
The most common problems I've seen:
1. Double-triple-check that the linking URL is to a "ping-able" post (not a page or the blog URL).
2. The post you publish the link from must be "public" (Settings-->Privacy check one of the first two settings). If your blog is private(three remaining settings), it doesn't send pings. You'll have to submit comments the old fashioned way, then. The receiving post must also be visible to the net.
3. The post is not published or is password protected.
4. Settings-->Discussion-> check "Attempt to notify any blogs linked to from the article (slows down posting.)"
5. Receiving post must have checks next to "Allow Comments" and "Allow Pings" in edit form.
While editing a post you can investigate if your post "pinged" by looking under Advanced Options-->Trackbacks for "Already Pinged".