I have a couple example posts I'm using to test out my new site design and so this bug is the result of a rather contrived post in Markdown. Still it seems it should work. I have the following:
1. Get Up
2. Read Blogs
The preview for that Markdown will place all the items in a single unordered list with bullets preceding each. Additionally it puts blank lines between Crackers and Beer and Get Up and Read Blogs. As I say it is a contrived example and probably not something most people would ever try to do in a blog entry, but it may be indicative of other issues with the list handling.