PHP Errors at the top of Admin page

I get a bunch of PHP warning messages at the top of my admin screen. I have updated all of my plugins, cleared my GoDaddy cache... can you let me know how to make these go away? I am not sure which plugin is causing it:

Warning: Illegal string offset 'sitemappath' in /home/content/a2pnexwpnas03_data01/50/3410650/html/wp-content/plugins/wpmu-dev-seo/includes/admin/settings/sitemap.php on line 224

Warning: Illegal string offset 'sitemapurl' in /home/content/a2pnexwpnas03_data01/50/3410650/html/wp-content/plugins/wpmu-dev-seo/includes/admin/settings/sitemap.php on line 228

Warning: Illegal string offset 'sitemap-images' in /home/content/a2pnexwpnas03_data01/50/3410650/html/wp-content/plugins/wpmu-dev-seo/includes/admin/settings/sitemap.php on line 232

Warning: Illegal string offset 'sitemap-stylesheet' in /home/content/a2pnexwpnas03_data01/50/3410650/html/wp-content/plugins/wpmu-dev-seo/includes/admin/settings/sitemap.php on line 236

Warning: Illegal string offset 'sitemap-dashboard-widget' in /home/content/a2pnexwpnas03_data01/50/3410650/html/wp-content/plugins/wpmu-dev-seo/includes/admin/settings/sitemap.php on line 240

Warning: Illegal string offset 'sitemap-disable-automatic-regeneration' in /home/content/a2pnexwpnas03_data01/50/3410650/html/wp-content/plugins/wpmu-dev-seo/includes/admin/settings/sitemap.php on line 244

Warning: Illegal string offset 'verification-google' in /home/content/a2pnexwpnas03_data01/50/3410650/html/wp-content/plugins/wpmu-dev-seo/includes/admin/settings/sitemap.php on line 248

Warning: Illegal string offset 'verification-bing' in /home/content/a2pnexwpnas03_data01/50/3410650/html/wp-content/plugins/wpmu-dev-seo/includes/admin/settings/sitemap.php on line 252

Warning: Illegal string offset 'verification-pages' in /home/content/a2pnexwpnas03_data01/50/3410650/html/wp-content/plugins/wpmu-dev-seo/includes/admin/settings/sitemap.php on line 256

Warning: Illegal string offset 'sitemap-buddypress-groups' in /home/content/a2pnexwpnas03_data01/50/3410650/html/wp-content/plugins/wpmu-dev-seo/includes/admin/settings/sitemap.php on line 260

Warning: Illegal string offset 'sitemap-buddypress-profiles' in /home/content/a2pnexwpnas03_data01/50/3410650/html/wp-content/plugins/wpmu-dev-seo/includes/admin/settings/sitemap.php on line 264