I published a post today too hastily and realized I had forgotten to put the trackback links in the trackbacks field. I have WordPress set to notify blogs when possible, but it never does. I went back into the post and added the trackback links and clicked save. None of the trackbacks went through. I realize that the blogs I trackbacked may have moderation enabled, but the links are not showing as Pinged under the trackbacks section. I tested sending a trackback to myself upon publishing, and it worked fine, so it is not an issue with trackbacks themselves.
I am on WP 2.3.3.