Apps :: Photos App No Longer Launches - Invalid Value For Registry

Apparently it is my turn: Photos app no longer launches (clicking on the icon does nothing; no error report in Event Log). Trying to double-click image files associated with Photos results in "Invalid Value for Registry" message box. No explanation as to for what value is "invalid" and why it is "invalid".

It appears that the damage is user-account-specific, meaning that Photos typically continue to work fine under different (undamaged) user accounts. So, the only known solution appears to be to create a new user account and set it up from scratch.

Considering that setting up a new account requires quite an effort, this is not a real solution but more of a last resort "loser's way out" kind of measure. Hence the question: any additional information/research about this error? What specific "registry value" is responsible for this problem? I see quite a few reports about this error on the Net, but most of them seem to settle with creating a new account.