I also have the same problem: my centre block is empty after I tried to install new modules (articles) in my xoops. Finally, I found out the setting of the following files/directories are not writeable:
1. directory uploads/
2. directory cache/
3. directory template_c/
4. mainfile.php
I went to the file manager and change the above file/directories permission to writeble and reinstall the module I want to use. Now I get my centre block displayed when I clicked at the Article menu.