Hi, i had this problem too when i updated my Windows 10!
I googled and found that Microsoft inserted bugs with startup directory, i tried all possibles thing and it didn't work!
Somebody found the answer, by using this registry key with 32bits registry part:
\HKEY_LOCAL_MACHINE\SOFTWARE\WOW6432Node\Microsoft\Windows\CurrentVersion\Run
... then you add a new key for PinballX ans insert your string in " quotes ". This should work now!