I have a similiar problem as Nikolakis using your simple SNMP get file. The community name doesn't seem to be to problem because I can change it in the device and it still doesn't work. I can get some OIDs to work and others won't return anything.
OID .1.3.6.1.2.1.1.1.0 - works fine. It returns the same OID, datatype, and then the value.
OID .1.3.6.1.4.1.21796.4.1.3.1.4.1 - doesn't work, it returns a different OID and nothing in the datatype or value.
I am not sure what to do. I am not sure why labview won't support SNMP, all I need to do is get one value from a device. Any ideas?