Scans post for links, checks if they are pingeable and sends pingbacks with results returned, improves chances of successful pings!
While some of the pingback error codes are self-explanatory, others can be a little confusing. There is a list of fault codes and some suggestions here: http://pingbackpro.com/support/#faultcodes
Unfortunately there isn't a great deal you can do about this, apart from sending an email to the owner of the blog you are pinging, you could try to find a similar resource that is pingeable.
Yes, actually. Pingchecker includes a workaround for a bug in the WordPress XML RPC server that can frequently return pingback fault 17, which basically says your post doesn't contain a link when it really does. A hidden div element is added to page containing the links in your post which makes them easier to find by the server code, allowing more pings to succeed.