I believe it is my usage of the Date() object. I am creating a new one every update in my system code ( it updates every 60 times a second ). I do this because I want a millisecond accurate clock useful for timers, animations, etc.
This is what's executed ever update:
// time reference
var Current = new Date();
// system loop here
step( Current ); // the local time variable gets passed to step
Any help greatly appreciated!