NA 9.0: OS analysis fails on Cisco 3550 running IOS <12.1(20)EA1

Hi all,

I am trying to upgrade IOS on a number of Cisco IOS devices through NA, but I'm not allowed because the OS analysis task hasn't been run. When I try to run that task, it fails with the following message:
"Error contacting device. SNMP may have timed out to the device or the credentials may be incorrect. Increase the SNMP timeout in the Admin Settings (Administrative Settings->Server->Software Image Management->SNMP Timeout) and/or check the SNMP credentials for the device."

The SNMP credentials have been confirmed, and the timeout setting is far greater than the time NA spends on completing the task and outputting the error message. The device also responds to SNMP queries when discovering the device, and snapshots are succcessful.

The problem occurs when trying to access devices running IOS 12.1(14)EA1a and older, but not on IOS 12.1(20)EA1 and newer.

Anyone else out there with a similar problem and - hopefully - a solution, or could this be a bug in the driver?