These problems have a single root cause which is with a particular MIB added to NV.
When creating a new dataset the MIB being used may expand fine in the Console MIBs tab to show the tables and OIDs as in this example with CISCO_POP_MGMT_MIB.
However when trying to use it for a new dataset it will fail to show any MIB tables.
In such a case there will be a dependency MIB causing the problem.
In this case it is DS1_MIB, and when clicking to expand it hangs on 'Loading...'.
Additionally this will result in the MIB Browser failing to load.
Where it should show the tree it will just show Loading...
Also the status bar at the bottom will have the error:
Unable to read MIB: [RedPoint][SnmpQL Driver] Unable to access mib service
Often but not always the D:\NetVoyant\logs\mibs.log file will have an error. When it does it will specify the MIB causing the problem.
omniORB: 2015-07-28 12:48:29.371000: WARNING -- method '_get_moduleTables' on: root/MIB<MODULE.DS1.MIB> raised the exception: IDL:omg.org/PortableServer/POA/WrongPolicy:2.4
Typically it is the Traps section of the MIB which is causing the problem for NV which can be removed to get things working.