I think it is my lg writer's problem, because with my pioneer the writing was ok, look at the log:
I 20:32:34 ImgBurn Version 2.5.0.0 started!
I 20:32:34 Microsoft Windows 7 Ultimate Edition (6.1, Build 7600)
I 20:32:34 Total Physical Memory: 2.095.608 KB - Available: 1.059.664 KB
I 20:32:34 Initialising SPTI...
I 20:32:34 Searching for SCSI / ATAPI devices...
I 20:32:34 Found 1 DVD