Are you connecting to the node as SNMP or WMI. One of the problems is that NPM/SAM still "prefers" SNMP in that if you scan your network with both sets of credentials and BOTH will work for a device, SNMP is used (and thus, mount points are not picked up). You need to convert those nodes to WMI (edit properties, change teh polling type, provide the credentials) and then re-scan the device for the new drives.
OR delete those boxes and re-discover them with any SNMP creditals DELETED from the scan.