It also doesn't work for me in Chrome on Win8. It does work in IE10, though.
I saw an issue also reported on here earlier today a few days ago. Sounds to me like a (new) canvas bug in Chrome.
There are unfortunately several workarounds for browser bugs in the HTML5 viewer. The AS3 Flash port was surprisingly very solid. I can't wait to share more info on that when it's time for another major release.
Cool app + site, congrats! Would love to use this to analyze my disc golf throws, and share with my fellow disc golfers.