I have a test set which contains five instruments which are accessed via IVI calls. NI MAX shows the Logical Names are all set and they are all assigned to the correct instrument drivers.
Everything was working fine. I could create and run TestStand IVI DMM, IVI Switch, and, IVI Tools steps referring to the IVI Logical Names in MAX. I could also create LabVIEW VI's with IVI calls to the IVI Logical Names in MAX.
One day I got an error from LabVIEW that the IVI Logical Name contained invalid characters. When I selected the dropdown list it was now empty (it had been populated before with the devices in listed in MAX). TestStand did the same, threw an error about IVI Logical Name contained invalid characters. Opening NI MAX, under the IVI, Logical Name branch all the logical names are still present and correct.
I assumed something had got corrupted, so I did a repair install of the IVI Compliance Package. No change. So I removed it completely, rebooted, and re-installed it. Again no change. I reloaded the IVI logical names from an XML file we have as part of the installation, but no dice.
Does anyone have any ideas? I would like to avoid a format and complete re-install from scratch if possible, but it might be the only solution? 
Thanks.