A Google Groups thread has confirmed reports from Jeremy Hylton of Google, that Google blog search, in some cases, has issues finding and returning new blog posts in Google Blog Search.

Jeremy explained that earlier on, there was an issue with Google crawling certain blogs. But then at the end of December they fixed that issue. Now, it appears there is an issue with the same type of blogs, where Google is missing random new blog posts from those blogs.

Here is how Jeremy put it:

I believe this all started in early November, when Google changed how they index blogs. In early December they vowed to fix it and then in late December, Christmas time, they thought they fixed the bulk of it. However, there are still issues that Google is aware of, including the issue mentioned above.

Forum discussion at Google Groups.