Not sure why there was a big break but Ep. 17 "I Will Follow You Into The Dark" will air on the 12th of this month. Here is a link to the airing dates left and quick summaries of them.
Yes episode 17 has aired tonight 12th March! You can watch Grey's Anatomy Season 5 Episode 17: "I Will Follow You Into the Dark" here: link I hope this sagot your question!