Hello,
I have found an bug in Forum Maintenance which occurs while SEO4SMF is enabled.
The picture is shown below:

Link: http://img61.imageshack.us/img61/4968/seo4smfbugbj2.jpg
How to reproduce?
1) Click on Admin center
2) Click on Forum Maintenance
3) Look for "Remove Old Topics" section
4) Check one of the boards (e.g. your Trash board)
5) Click REMOVE NOW
6) Click OK
7) Tadaaa!!!

Regards.