Problem with CSS media queries viewed through IEMobile 10

I found an issues with my Plone responsive theme on an IE 10 Mobile 
browser when the Plone site is run in production mode. I've checked with 
a small number of mobile browsers - Firefox, Chrome and Safari which 
seem OK.

I use the viewport fix which can be found in the Twitter Bootstrap 
responsive utilities, which includes javascript to embed 
<style>@-ms-viewport{width:auto!important}</style> in the head; and css 
media queries.

I've noticed the problem can be "fixed" by removing the 'caching 
allowed' and 'merging allowed' on the css resource which contains the 
media queries.

Is this a bug?

Simon

Note: Version Overview

     Plone 4.3.4.1 (4309)

     CMF 2.2.8

     Zope 2.13.22

     Python 2.7.8 (default, Oct 23 2014, 21:36:28) [GCC 4.1.2 20080704 
(Red Hat 4.1.2-55)]

     PIL 2.3.0 (Pillow)




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