This may not actually be considered a bug. I can't replicate it with any frequency. It seems to be random, but it does happen randomly about 1 in 10 times. When I'm in Advanced Input mode, I drag and drop folders/files, create folders I want, etc. I X close the Advanced Input window, but instead of closing and ImgBurn doing its calculations on the input, the window sometimes goes minimized to the tray. I just open the minimized window, X close it again, and everything proceeds as it should, with the window closing and the calculations performed.
It's actually been doing this for years and I just lived with it since I never could replicate it except randomly. But, after I got it just a moment ago, I thought I'd post it.