The site is displaying perfectly. Please look at all the observations below before suggesting; it may rule out some possibilities.
The WordPress Database Backup plugin produces ZERO-BYTE files.
The automatic upgrade to WP 3.1.1 gives this error:
Could not create directory.: /home/motorbik/public_html/wp-content/upgrade/wordpress-3.tmp
Trying to upgrade any plugin gives this kind of error:
An error occurred while updating Ozh' Admin Drop Down Menu: Could not create directory. /home/motorbik/public_html/wp-content/upgrade/ozh-admin-drop-down-menu.tmp.
I looked at the upgrade folder, and it has the same 755 permissions as other folders, and is the same on a site where this problem does not exist.