IntegraMOD

Check post and topic tables or maybe one of the other features, I have a member who has lost approximately 1000 post since I ran some of the Database Maintenance features, has also updated some other members too.

What would be the reason for them losing posts?

I know this sounds a bit vague but am not sure which Database Maintenance procedure I did that actually removed the posts <img>

Just a suggestion, but try going to ACP>Forum Admin>Forum Management, and click on Resync.
It might be that the posts are still there, but your forum needs to be resync with the database to connect the dots so to speak.

Try it and let us know the results.

There is also a Syncronize forums and posts in the DB maintenance.
Did you do this?
Maybe you pruned the forum in the past and the counts were readjusted to reflect post pruning.