OS X 10.10.1 Yosemite was recently deployed by Apple and the release was supposed to fix a lot of problems, including some relating to Wi-Fi performance. Unfortunately, however, it appears the update may have caused its fair share of errors, too.
Folks who have already downloaded the update are noting in both Apple and Google support forums that the update is causing the YouTube Player to report an error inside of Safari. “Last night I updated Yosemite to 10.10.1 and now all of a sudden Safari Version 8.0 (10600.1.25.1) won’t play any YouTube videos,” one commenter complained. “All I get is a black screen with a little audio clipping.”
Another user noted that, after downgrading the OS, he or she was able to again play videos without issue. It appears that YouTube still works if you have Firefox or Chrome installed instead, but that’s not very helpful for folks who prefer Safari. Hopefully Apple can create a quick fix, but in the meantime you may want to hold off updating your system.