After upgrading zabbix from 1.6.5 to 1.6.6 zabbix_agentd reports the following errors in logs:

Linux-Systems:

21763:20090910:020718 Can't open JSON object or array ""delay":"5","lastlogsize":"0"},{"key":"net.tcp.port[,3551]","del"

Windows-Systems:

9344:20090910:022607 Can't open jason object
9344:20090910:022807 Can't open jason object
9344:20090910:023007 Can't open jason object
9344:20090910:023207 Can't open jason object
9344:20090910:023407 Can't open jason object
9344:20090910:023607 Can't open jason object

It seems to be the same error as reportet in ZBX-668 which should be fixed in 1.6.2 - But now it seems to be back...

Already reported also in forum: http://www.zabbix.com/forum/showthread.php?t=13969