Not sure what to tell you unless you actually provide more info, like for example, Gantry version you use, Joomla version, part of the log entries so we can see what is going on
Joomla 3.2.3, Metropolis template latest version and gantry.php, rokcommon.php and rokupdater.php are always full of:
2014-04-07T10:25:41+00:00 NOTICE - Can't identify browser version. Agent: Mozilla/5.0 (iPhone; CPU iPhone OS 7_1 like Mac OS X) AppleWebKit/536.26 (KHTML, like Gecko) GSA/3.2.1.25875 Mobile/11D167 Safari/8536.25
2014-04-07T11:11:39+00:00 NOTICE - Can't identify browser version. Agent: Mozilla/5.0 (Symbian/3; Series60/5.3 NokiaN8-00; Profile/MIDP-2.1 Configuration/CLDC-1.1 ) AppleWebKit/533.4 (KHTML, like Gecko) NokiaBrowser/7.4.2.6 Mobile Safari/533.4 3gpp-gba
and I have found a solution in commenting the \libraries\joomla\environment\browser.php line 464
// JLog::add("Can't identify browser version. Agent: " . $this->agent, JLog::NOTICE);
in order to disable this triple logs.
Maybe the RT development team will provide a better solution.