Thank you for the replies. However, I already have both "Cancel AutoPlay" and "Disable Media Change Notification" checked on tools>settings>device.
All three OS options in the same panel are enabled as I haven't touched them, since they're OS and not ImgBurn options, and since I want autoplay enabled in the OS, as it already was (if I disable them through ImgBurn, autoplay will stop working altogether as a result).
This only started happening after I upgraded ImgBurn from an older 2.5.x build to the current one. It's like the tray is being cycled after a burn finishes and ImgBurn closes (automatically as per the corresponding option), despite the fact that the tray isn't physically ejected (as I also have that option disabled in ImgBurn).
Any more ideas ? Thanks again.