If setLineDash is used at some point during a Canvas paint callback, all paths will use dashed lines. It's also unclear how the dash pattern can be disabled. setLineDash([]) should work as far as I know, but it does not here.

setLineDash([99999999999999]) seems to be a temporary workaround at least for shorter paths.

var c = getContext("2d");
c.reset();
c.beginPath();
c.lineTo(100,100);
c.stroke(); // gets the 5,5 pattern defined below!!! 

c.beginPath();
c.setLineDash([5,5]);
c.lineTo(-100,-100);
c.stroke(); // gets the 5,5 pattern

c.beginPath();
c.setLineDash([]);
c.lineTo(13,14); // still the 5,5 pattern
c.stroke();