Css editor generates error message in header on all pages

I’m working on a site that hosted by a university. They have automatic updating of WordPress which already broke the site once. Now, trying to activate the CSS editor results in the following error message being displayed on all pages:

Warning: is_readable(): open_basedir restriction in effect. File(C:webrootwordpress/wp-content/plugins/C:webrootwordpresswp-contentpluginsso-css//languages/so-css-en_US.mo) is not within the allowed path(s): (c:webroot) in C:webrootwordpresswp-includesl10n.php on line 561