You can’t cancel / close it because if the I/O command sent to the drive never gets processed, ImgBurn is not in control.
As soon as the driver/drive returns success or failure, ImgBurn will be back in control and will deal with your request to quit.
I/O is quite synchronous, that’s why other programs don’t work - the command the system is sitting on is holding everything up. If it’s a USB drive just unplug the thing and windows will probably spring back to life. The disc will be toast but then it would be anyway.
Are you using decent media? (What MID’s?)
Is the firmware on the drive up-to-date?
What speed are you burning at?