I suspect this question might be better suited for either the CVI or LabVIEW board. I think you are either using ActiveX from a .NET environment to automate LabVIEW. If so, could you provide some additional information on what you are trying to accomplish? I suspect that you are attempting to run a VI using automation and close the VI afterwards, but would like to keep LabVIEW open so subsequent calls to run the VI will take less time to load. If this is the case, you should open a reference to the _Application class, once this is open you can use the methods mentioned above (open VI reference, etc...) and finally use the _Application method "Close" to close LabVIEW. I'm not exactly sure why your close front panel method is not working, but perhaps if you provide a snippet of the code in the LabVIEW board myself or someone else in the LabVIEW community can take a look at it and see what exactly is going on.
Hopefully this helps! Please let me know if you have any additional questions.