Ping.fm sometimes not posting to Twitter

Normally my posts go to Twitter, but lately (10/20 and 10/21) some of my posts just didn't get posted to Twitter. Is there something I'm doing wrong? What does ping.fm do for Twitter posts if the length is longer than 140 characters (truncate?). Is there a log of success/failure in posting somewhere so I can go look what happened to my missing Twitter posts from ping.fm?