That's weird, Before looking at the images on your site, I could not see them on the forum, now they show up!?
It looks like you have the Arduino serial monitor attached to the com port. Only one device on the system can use the port, so if Arduino is attached, you won't be able to get Grasshopper attached. The access denied error is telling us the same thing: that something else is already talking to the serial port.
The other thing I noticed is that there was an error message on the window in the background (near the bottom center of the screen). It is referring to a recursive call. I'm not sure if this is related to the issue you have that seems like the code loops forever, but it could be.