If external script returns 0 then I see in zabbix server log:

19516:20120817:093623.552 item [Lud-cr2801-1:pingloss.sh[-c 20, -q, -B1, -r1, -b1500,

{HOST.CONN}]] became not supported: Received value [0]
is not suitable for value type [Numeric (float)]


If script returns 0.0 all is OK:

19516:20120817:095325.202 item [Lud-cr2801-1:pingloss.sh[-c 20, -q, -B1, -r1, -b1500, {HOST.CONN}

]] became supported

I think this is wrong.