Possible conflict with Jetpack Custom CSS CodeMirror editor

Hi,

When loading Jetpack’s Custom CSS module (Appearance->Edit CSS), the editor is not loaded. Disabling the Use Google Libraries plugin makes the editor reappear.

It seems this Jetpack module prefers to use a CodeMirror editor, but can fall back to a textarea if the CodeMirror editor is not available. It seems that in my case, it hides the textarea with id=”safecss”, because class=”hide-if-js”, but fails to load the CodeMirror editor, resulting in no editor at all.

Strange thing is, I only see this behaviour on my live webserver, not on the local copy I’m running on MAMP.

For both, I see GET requests for codemirror.min.css, use-codemirror.min.css, codemirror.min.js and use-codemirror.min.js being sent to my webserver/localhost (so not Google), all returning 200 OK.

This is what Firefox Page Inspector shows me:

From webserver (not working):

<textarea id="safecss" class="hide-if-js" name="safecss">
...
</textarea>
<div class="clear"></div>

From local MAMP (working):

<textarea id="safecss" class="hide-if-js" name="safecss" style="height: 188px; display: none;">
...
</textarea>
<div class="CodeMirror cm-s-default CodeMirror-wrap" style="height: 270.5px;">
...
</div>
<div class="clear"></div>

Thanks,
Peter

Webserver (not working):
Apache/2.2.22 (Debian)
PHP 5.4.35-0+deb7u2

Local MAMP (working):
Apache/2.2.26
PHP 5.4.26

Same for both:
WordPress 4.0.1, JetPack 3.2.1, Use Google Libraries 1.6.2
Other plugins: Akismet 3.0.3, Contact Form 7 4.0.2, Enable Media Replace 3.0.1, Google Analytics by Yoast 5.2.2, Jetpack by WordPress.com 3.2.1, Maintenance Mode 5.4, mqTranslate 2.9, Multipage canonical fix (own), Twenty Eleven Theme Extensions 1.2, Use Google Libraries 1.6.2, User Role Editor 4.17.3, WP-Optimize 1.8.9.7, WP Minify Fix 1.3.4 (problem also occurs when WP Minify Fix is disabled), WP Super Cache 1.4.2.
Theme: Twenty Eleven 1.9 child theme
Client used: Firefox 34.0.5

https://wordpress.org/plugins/use-google-libraries/