The top menu was displayed in Firefox and Chrome but was missing in any version of IE.
We've added X-UA-Compatible Meta Tag in index.php file, in clarion template folder.
Any of the following solved the problem for IE9 but not for IE7 & 8, the top menu is still missing.
<meta http-equiv="X-UA-Compatible" content="IE=EmulateIE7">
<meta http-equiv="X-UA-Compatible" content="IE=7">
<meta http-equiv="X-UA-Compatible" content="IE=8">
<meta http-equiv="X-UA-Compatible" content="IE=9">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
We've removed Akeeba Backup Lazy Scheduling and it worked.
However, we still had to keep
<meta http-equiv="X-UA-Compatible" content="IE=edge">
in clarion template index.php file, to make it work for IE8.