I had the exact same issue. I finally figured out that the following 3 fields in the “wp_posts” table had to be set to “Allow Nulls”:
1) to_ping
2) pinged
3) post_content_filtered
I’m not sure what tool you are using to access you DB but I use Aqua Data Studio (freeware). I just did an “Alter Table” on “wp_posts”, located the 3 fields listed above and then selected “Allow Nulls” for all three.
Hope this helps.
