IPropertyStore interface not called in a property handler - windows

Question

I am developing a property handler implementing IPropertyStore and IInitializeWithFile, testing on Win 8.1 x64. Property names were previously added to the system using a .propdesc file properly registered using prop.exe.
I used PROCMON.EXE to monitor the events when I re-indexed my files on disk. SearchPrototocolHost.exe loads the protocol handler, initializes it properly with IInitializeWithFile (the properties from the file seem to load OK from the file) then proceeds with PSCreatePropertyStoreFromObject presumably to retrieve the IPropertyStore interface and start retrieving the properties from the file.
Then nothing else happens, the methods from IPropertyStore are never called. Instead, SearchPrototocolHost.exe issues a CreateFile on the file to be indexed again with "Open Reparse Point", fails at getting a QueryRemoteProtocolInformation, closes the file then proceed with the next file to index.
Why does my property handler fail (is it a security issue, etc.?)?

Answer 1

It looks like one needs to add to the registry entry:
"HKLM" "SOFTWARE\Microsoft\Windows\CurrentVersion\Shell Extensions\Approved" {My_CLSID}
where My_CLSID is the GUID of my property handler!
I don't know if this is a specific requirement for handlers using IInitializeWithFile as an extra security precaution.
After three weeks of banging my head against walls, now I can "hear" the IPropertyStore methods (using MessageBeep...) when they are called by Explorer. Never mind that they crash Explorer, at least I know that IPropertyStore is not blocked!