I'm experiencing the same problem with the black note screen right now after updating to 6.17.5.8273.
I have:
1. signed out and signed in
2. uninstalled and installed and restarted the computer
3. Set Hexidecimal Value to "0" - signed out and signed back into Evernote
None of these have worked. Luckily I have Evernote installed on my laptop as well which I will not be updating until I can get this issue resolved.