Have you uploaded? Can you provide a link please? I use this tool often, and have it working in I.E., FireFox and Opera....checking....yes it works in Opera, just can't 'click & drag' the window.
Ok, I just tried the program myself, and for the very first time...I get the same error as you! It used to work.
Until CC gets a fix for this, you can edit the .js file that is created. It has an x and y section (written Top and Left). Just change the numbers and save...record what works because using the program with overwrite those back to -1 or 0.
You can open the .js file in your favourite text or html editor
E-Learning Specialist
www.mainsites.ca is my website, and yes, some of it is crappy.