I have a wordpress.org blog configured with pingomatic.com. I verify my site on Google webmaster tools, all my post are indexed on the "normal" google search but no one on Google BlogSearch. I manually visit pingomatic.com many times and I also visit http://blogsearch.google.com/ping. I type the exact title of a post and I choose to see posts from the last month. Nothing.
You're pinging an update service, you're presumably also publishing a feed, and you've done the manual submission, after which they'll "do their best to add it to their index as quickly as possible." You've covered your options. Now you wait. Google almost never make any specific statements about how long anything will take.
This assumes, of course, that you're not telling them not to index you via your WordPress settings, for example.
There's also an older(so maybe no longer applicable) thread in which a Google rep said that a missing robots.txt file would also cause them not to crawl. Which is weird, but if you don't, just creating a blank one won't hurt anything, anyway.