[WPMU DEV SEO] sitemap.xml not being generated

It seems I have a similar problem as ozbod in this possibly related thread. WPMU DEV SEO is not generating any sitemap.xml files for the main site or subdomains. It was mentioned in the thread linked above that this issue could stem from an issue with a modified vhost.conf file. Here's what I have.

Contents of vhost.conf:
Domain modified for slightly more privacy... :wink:

ServerAlias *.domain.tld
<Directory /var/www/vhosts/domain.tld/>
AllowOverride FileInfo Options
php_admin_flag safe_mode off
</Directory>

Please see attached screenshots for more info. Note that screenshots are showing config of main site only - no subdomains. Directories shown in screenshots have permissions set to 755, with ownership set to the username and group set to apache (which is what apache is running as). Possibly related issue: After upgrading CentOS, WordPress asks for FTP auth info when doing "automatic" updates to plugins.

Server Config:

WPMU DEV SEO 1.1.2
Theme: WooThemes Canvas 4.1.4, Framework 4.1.5
WordPress 3.1.3 Multisite (4 subdomains, 1 for each of client's real-worldd locations)
PHP 5.1.6
CentOS 10.2 VPS

Please let me know if any other config info is needed.