What is your OS?
WIN 10 64, however, I think I got it.
I changed InvokeProgID to Adobe.AdobeLightroom64 - the 64 was not there.
Yep. Glad it works for you now.
This problem should be fixed in the install. I don't want to mess with the registry in Windows 10. Now a year later (after this report) I have purchased Lightroom 6 upgrade and the problem still exists. I had to uninstall and go back to 5.7.