I am seeing something similar. I am using 1.2.3 I had mine set to most recent post>medium and the rest of the posts>small. Now, when masonary is enabled, all blog excerpt boxes are the same size, I have two columns and the load more text message is missing. The blog also doesn’t load anymore excerpts beyond the first 10. I have been using WP 4.0.1 with no problems till today (at least when I noticed it).