Hi Marc,
It seems to be a bad configuration of Cache plugin or a plugin conflict.
Try the following:
1) Disable caching plugin and check site.
2) Disable all plugins and check site if 1) doesn’t work.
When checking site, check in private browsing each time to prevent the browser from serving old local cache.
Also, upgrade theme to latest version http://themonic.com/forums/topic/how-to-upgrade-iconic-one-pro-responsive-theme-to-the-latest-version/
If after doing the above issue is still not resolved, send email with login details to [email protected] with a link to this thread.