Before you ask ... I have looked everywhere for a solution, even drupal.org but nothing so far seems to work.
Here's the problem:
I developed a Drupal site (custom child theme for Zen) and on the development server everything looks fine in all browsers.
I did a test migration to another server before the launch. This move went well and everything looks fine in all browsers.
Then I moved the site to its live server where everything looks fine in all browsers except Internet Explorer which is not loading the stylesheets.
I know Drupal is known for generating many stylesheets and Internet Explorer will not load them if there are more than 31 (I believe) of them, but I did set the "Aggregate and compress CSS files" feature and clear the cache. This did not seem to help.
I still have some work to do (the site loads slowly) so I apologise for that. The official launch of the site is only a week away and I really need an answer to this dilemma.