I'd be amazed if you could burn 5 with ImgBurn, have them all fail, burn 1 with nero, have it work and then burn 5 more with ImgBurn and have them all fail.
The odd one here and there is just drive / firmware / media issues.
The burn has started - which means its not a program issue. After that point, there is only one way to get the drive to write stuff - by sending lots of write commands. In that sense, which program you use makes no difference.
Manufacturers tend to do more work (firmware wise) with current media - i.e. stuff that burns at 16x.
So take spinningwheels advice and try out some newer media.
The cdfreaks forums will give you a good idea of what works and what doesn't on Liteon drives.