I have WordPress set up to ping the default rpc.pingomatic.com. Posting is quick, but my new posts don't appear on sites such as Technorati or Google Blog Search. If I visit http://www.pingomatic.com and enter my details manually, my new posts appear on those sites within minutes.
I've installed Christian Davén's Smart Update Pinger plugin, which keeps a logfile, and it shows, "http://rpc.pingomatic.com/ was successfully pinged (extended format)"
Does anyone have any ideas as to what could be wrong?