Today a coworker brought me his Macbook with Mavericks and Safari up to date, and we replicated the problem. I did a quick test upgrading jQuery Countdown (the plugin we use to display the track progress counter) to the last version and the problem seems to disappear.
Please test it too:
go to the plugin's page and download it, then exctract
jquery.countdown.js from the .zip archive. Then upload it via SFTP (user: root, passw: rune) in this folder:
var/www/js. Let me know if the problem completely disappears.