Suggestions:
- Could be a bad disc. Try a Verbatim DVD+R DL disc instead.
- Your drive may not be compatible with those discs. Try a firmware update.
- There may be a bad filter driver installed or a conflict with another piece of software that is interfering with communication between ImgBurn and the drive. In ImgBurn, use Tools/filter driver load order to see what's installed; clear out anything you no longer need.