ImgBurn defaults to using DAO as the write type, Nero might use Incremental - depending on your settings.

Perhaps that drive prefers the latter?

You can change ImgBurn to use Incremental in the settings.

In any case, if anything is producing unreadable discs, it's the drive. The software has no control over the burn quality, it simply sends the data to the drive. If an I/O command gets stuck, blame the drivers or the drive that's supposed to be processing it. It should be a simple case of 'Nope, I don't like that' or 'Ok, I'll process that' - where the 'Arrrggh I don't understand, I'll just hang' came from, I've no idea. ImgBurn will always wait until it's had a 'success / failure' reported back. If it doesn't get one straight away, it just continues waiting until it does.

Don't worry about rebooting, closing everything down etc. I never do. Use your PC as you would do at any other time - browse the internet, write documents, it's all fine!
Just don't do daft things like defragging your hdd whilst trying to burn an image from it or play the latest 3D games that keep your CPU at 100% all the time.