[Plugin: WordPress SEO] Cannot save page/post on multi-site

Hi;

I am using WordPress SEO on a WP MU site. This is a brand-new installation with few additional plug-ins.
When I try to update a published page/post I need to click the “update” button twice before the page/post attempts to update. When the page reloads all changes are gone and I see the text before it was saved.

In addition I see these error messages:

Warning: require(/kunden/colognehosting/rp-hosting/KXXXXX/AXXXXX/wp-content/plugins/wordpress-seo//admin/linkdex/TextStatistics.php) [function.require]: failed to open stream: No such file or directory in /kunden/colognehosting/rp-hosting/K11152/A12176/wp-content/plugins/wordpress-seo/admin/linkdex/linkdex.php on line 6

Fatal error: require() [function.require]: Failed opening required ‘/kunden/colognehosting/rp-hosting/KXXXXX/AXXXXX/wp-content/plugins/wordpress-seo//admin/linkdex/TextStatistics.php’ (include_path=’.:/usr/local/lib/php’) in /kunden/colognehosting/rp-hosting/K11152/A12176/wp-content/plugins/wordpress-seo/admin/linkdex/linkdex.php on line 6

The double slahes // (bold by author) are obviously wrong, but I’m clueless where they are coming from.

The path has been modified. XXXXX replaced original text.