17
I seem to have the problem when I go in and manually delete comments from my news posts that were made by spam accounts.
For example, just tonight, I saw I had a few new spam accounts on my site. Some of them had no posts, so I just deleted their accounts. However, a couple of them made comments to my posts in the news module. I decided to delete the comments before I deleted the accounts. As soon as I deleted just one comment, all the post counts for every member on my site went to -1.
If it makes any difference, the only module on my web site where members can post comments or ANYTHING at all is the news module. Only admins can create new News posts. I can run the script that was linked up on page one and it sets all the post counts back to what they should be.
I just thought I'd throw this info out there in case it helps anyone else.