I have recently updated everything in CiscoWorks to 2.6. RME 4.0.5.
I run the hardware inventory and there are several switches that have not serial number reporting. 2900 and 2950 mostly. Some of the serials report but most do not. I have verified that they are all on the same IOS and none of them have the snmp-server chassis-id command in them.
Kiwi reports everything fine