If a system hang is observed during HP SUM discovery and the system is connected to external storage, in most cases disconnecting the external storage should resolve the issue.
If discovering an ESXi 5 server, make sure you have installed the CIM providers from HP. You may download this within the "Offline Bundle Utilities" on ESXi 5 server downloads from the HP support website at http://www.hp.com/support, or they come already bundled in the HP custom ESXi image