Hi Shannymara,
The "bug" you're referring to is a result of posts being deleted from any particular thread showing this problem; apparently the database does not decrement the value in the field that keeps track of the number of posts when deletions occur. Tho' I don't know what the relevant field is named nor the table in which it resides, if this site is a typical LAMP-based forum (Linux, Apache, MySQL, Php), then it's not that difficult to access the database using tools such as MySQL Administrator to manually correct the increment. Of course, you need admin access to the database to do so...