For some strange reason, my computer suddenly doesn't show certain unicode characters anymore! I have no idea what happened.

Affected applications include Windows Explorer (should be Japanese characters), Google Chrome (should be a heart), and Winamp (should be stars):

Russian, German etc. characters are displayed normally. Chrome also displays Japanese script on websites, but not in the GUI. How can I fix it?

Update: I have tried to use System Restore to fix it. I needed to go back in time quite a while because the most recent restore points didn't solve it so I used one from the middle of November. After that restore, Unicode symbols were displayed again. Then I updated my system with Windows Update again because those were removed during the restore. After that, the error occurred again! I then did a restore to a point before my new updates, but the error persists, and the old restore point (which I used before) is gone and there are currently no other snapshots of the system. Any suggestions on what to do now?

Update 2: I could find a workaround:

Control Panel ? Region and Language ? Administration ? Change Language for Unicode-incompatible programs to Japanese (Japan).

All mentioned programs display their symbols correctly again. However, I don't consider this a fix because these programs are not usually Unicode-incompatible, and it also leads to some (non-serious) artifacts in some programs. I still welcome an answer that tells me what went wrong here and how to fix the issue.