layout compatibilty problems with simple:press

Hello,
I’ve just installed Simple:press, the popular plugin that turn your wordpress blog into a brand new forum.
So, my problem is that it shows the forum interface twice.. Here you can see the problem:
http://produciconnoi.altervista.org/blog/forum/

How can I “delete” the first forum? I want just a normal blog with the forum inside like: http://simple-press.com/support-forum/

I’ve tried different themes but nothing solve this problem.
Can you help me please?

Thanks
Luca