I've imported my site from wporg and only a partial list of posts are showing up in the dashboard. When I reimport, it says, "already exists." I can even see the posts in the main dashboard under Recent Comments, but when I click the link, it just goes to the list of posts, not directly to the post. So the posts are in the system, they're just not sticking.
I thought maybe this was a problem importing from 2.6, but I set up another blog and imported fine from 2.6 to 2.9, so I'm thinking this is an MU problem. Importing from 2.9 to MU didn't help things.
Repairing the database and disabling all plugins didn't work.