Some trouble with update interval

[frolz]

I use zabbix 1.4 with mysql 4.1.21

I have Item with update interval 30 sec. Item have type snmp agent v1.

When i look "Values of specified period" in "Monitoring -> Latest data -> graph -> Values of specified period", i see:

Timestamp
2007.Jun.10 18:07:31
2007.Jun.10 18:06:01
2007.Jun.10 18:04:31
2007.Jun.10 18:03:01
2007.Jun.10 18:01:31
2007.Jun.10 18:00:01
2007.Jun.10 17:58:31
2007.Jun.10 17:57:01
2007.Jun.10 17:55:31
2007.Jun.10 17:54:01
2007.Jun.10 17:53:01
2007.Jun.10 17:51:31
2007.Jun.10 17:50:01
2007.Jun.10 17:48:01
2007.Jun.10 17:47:01

etc

Update interval is not 30 sec always.
Why? I have not answer...

When I use snmpget, i have answer from device always.

Addition info:
Store value --- Delta

zabbix_server.conf
Server=5
StartPollers=64
StartTrappers=64

Server:
2xIntel Xeon 2.8 with 8Gb memory.
CPU usage ~5%
la < 1

[Alexei]

How many active items and hosts you have?

[frolz]

I set status 'Not monitored' for all host, except this one.
Now, i have 1 host with 9 items.

4 item of 9 with trouble. (Items with troubles are counters for traffic, other are not).
Other Items updates regulary.

All item are snmp v1 agents.

[frolz]

There was trouble with snmp counter32, because it wraps around and starts increasing again from zero beetwen polling time.

Thread closed.

Thanks all.

[Alexei]

All right, thanks for the explanation.

[andydouth]

IS there a workaround or is this fixed in any version?

[Alexei]

There is nothing to fix as far as I can see.

[andydouth]

So we can't use MIBs that require counter32 type?

[Alexei]

So we can't use MIBs that require counter32 type?

Why?! It is perfectly supported.