Unfortunately, that has been happening some lately.  The developers are working on it.  It usually starts working again but sometimes it can take a while.  It is supposed to be a 3-minute block find time but it actually goes faster... especially after a long freeze up.  I think it still averages out but the devs should be able to do something to make it smoother. 

Difficulty is low and for now it seems the blocks are flowing.  Good time to mine B-hash.