Yep. You going have to throw out the file /YourHardDrive/Users/YourUserName/Library/Preferences/com.apple.finder.plist . Then reboot and upon the reboot run TinkerTool and set the Font changes again. Then reboot one more time.
Thanks, however there isn't a "Library" folder in /YourHardDrive/Users/YourUserName/ on my Macbook. There is this: /YourHardDrive/Library/Preferences but there isn't a com.apple.finder.plist file in that location. Finder search says there's no such file on the HD.