Actually, i'm not identify conditions, but in some cases in IE when change css property (through 'css' or 'animate' methods) arises error at line 5899.

#!cpp
fx.elem.style[ fx.prop ] = (fx.prop === "width" || fx.prop === "height" ? Math.max(0, fx.now) : fx.now) + fx.unit;

It happens when property fx.now is NaN. Problem was solved when I wrap this line into the try-catch block.

#!cpp
try {
	fx.elem.style[ fx.prop ] = (fx.prop === "width" || fx.prop === "height" ? Math.max(0, fx.now) : fx.now) + fx.unit;
} catch (e) {}