I have reported this issue to Boonex, and their reply is:
'You need to edit the 'when' column values in the 'pre_forum_post' table for the posts with the wrong dates.'
Below is the report from my PhpMyAdmin from the 'menu' in 'pre_forum_post':

Host: localhost
Database: mydatabase
Generation Time: Apr 23, 2008 at 09:26 AM
Generated by: phpMyAdmin 2.11.4 / MySQL 4.1.22-standard
SQL query: SELECT COUNT(*) AS `Rows`, `when` FROM `pre_forum_post` GROUP BY `when` ORDER BY `when` LIMIT 0, 30 ; see more
Rows: 1

Rows when
1 1206969070

I couldnt edit the numbers at the bottom. Anyone who finds a solution, pls post it here.

Thanks