This issue has finally been resolved (thanks Shelley), by changing the ThreadPoolPercentSocketReaders parameter in the config.xml.template file to "75".
Code:
<Server IIOPEnabled="false"
JDBCLogFileName="/opt/otm55/logs/weblogic/jdbc.log"
JDBCLoggingEnabled="false" ListenAddress="x.x.x.x"
ListenPort="7001" Name="gc3-server" NativeIOEnabled="true"
ServerVersion="8.1.4.0" TunnelingEnabled="true"
StdoutSeverityLevel="16" ThreadPoolPercentSocketReaders="75"> --Chris