Does your site have links like:
http://.../course/view.php?id=377&MoodleSession=b3i20qk970m1t92b2t2v1v2t90
on it's front page?
That might have an affect on any browser ... any platform.
Edit the links and remove the &MoodleSession ....
In browser, clear all cookies and cached pages.
On a 2.4.x server there is also a "purge all caches".
"Moodle can cache themes, javascript, language strings, filtered text, rss feeds and many other pieces of calculated data. Purging these caches will delete that data from the server and force browsers to refetch data, so that you can be sure you are seeing the most up-to-date values produced by the current code. There is no danger in purging caches, but your site may appear slower for a while until the server and clients calculate new information and cache it."
To find the link, login as admin level user and in the Site Admin Menu on the front page use the search box for 'purge'. The link will be the last item on the returned search page.
'spirit of sharing', Ken