Missing Data / snmp get timeout for host

[paleogryph]

I have been using 0.8.7g(with all current patches) since July of 2010. Everything has been working fine. Starting today, there are "bands" of missing data, from every device. The timing of the missing data bands is the same on every device. So I have assumed, perhaps incorrectly, that this is the poller.

The errors in the log are:
01/18/2011 04:50:08 PM - CMDPHP: Poller[0] WARNING: SNMP Get Timeout for Host:'device', and OID:'.1.3.6.1.2.1.2.2.1.16.2'
01/18/2011 04:50:08 PM - CMDPHP: Poller[0] Host[6] DS[45] WARNING: Result from SNMP not valid. Partial Result: U
01/18/2011 04:50:08 PM - CMDPHP: Poller[0] WARNING: SNMP Get Timeout for Host:'device2', and OID:'.1.3.6.1.2.1.2.2.1.10.2'
01/18/2011 04:50:08 PM - CMDPHP: Poller[0] Host[6] DS[45] WARNING: Result from SNMP not valid. Partial Result: U
01/18/2011 04:50:09 PM - CMDPHP: Poller[0] WARNING: SNMP Get Timeout for Host:'device 3', and OID:'.1.3.6.1.2.1.2.2.1.16.2'

etc; etc;...

I have rebooted a few times with same results. I set poller.php to run as follows in /etc/crontab:
*/5 * * * * cactiuser php /var/www/html/cacti/poller.php --force > /dev/null 2>&1

I added the "force" as per suggestions seen in these forums.

The errors in the log are still recurring and data is still intermittent from all devices.

I ran all the patch updates successfully and rebooted with same results.

Any suggestions?
TIA

[gandalf]

Force won't help.
Does the poller end within time during those "dropout" periods?
R.