It would seem that HP's SIM Agent is failing for some reason. I would recommend uninstalled and reinstalling the latest version of the System Insight Manager Agent itself, as well as the WBEM providers. You may be encountering an issue in an earlier version that was addressed in the latest. 10.0.0.0 is the latest version, if you're already running v10.0.0.0, then obviously that doesn't resolve the issue. If that's the case, I would switch the polling method for the node from SNMP to WMI, which is extremely unlikely to suffer from this issue. Just make sure you have installed the appropriate WBEM providers before changing the polling method for the node from SNMP to WMI.
If that's not possible so some reason, I would recommend contacting HP support for assistance. You can provide them a MIB walk from the device working vs when it's not working, as seen in SAM. The difference between these two MIB walks should be very significant and easily noticeable.