Are u used the last version and show your log please
I precise launching as admin, have free space on all HDD and try with serial at the beginning of file name.
19:39:06 - TwilightBoxart - Version 0.7.0.
19:39:31 - Started! Using width: 168 height: 130. Scanning G:\NDS_Roms_32Go\Roms..
19:39:31 - Searching art for 007 - Quantum of Solace (EU).nds..
19:39:35 - Could not find boxart. (404)
19:39:35 - Searching art for 0413 - Tetris DS.nds..
19:39:39 - Got it!
19:39:39 - Searching art for 7 Wonders of the Ancient World (EU).nds..
19:39:40 - Got it!
19:39:40 - Searching art for Advance Wars - Dual Strike (EU).nds..
19:39:42 - Could not find boxart. (404)
19:39:42 - Searching art for Age of Empires - Mythologies (EU).nds..
19:39:48 - Got it!
19:39:48 - Searching art for Age of Empires - The Age of Kings (EU).nds..
19:39:52 - Got it!
19:39:52 - Searching art for Ankh - Curse of the Scarab King (EU).nds..
19:40:00 - Got it!
19:40:00 - Searching art for Arkanoid DS (EU).nds..
19:40:05 - Got it!
19:40:05 - Searching art for Assassins Creed - Altair Chronicles (EU).nds..
19:40:09 - Could not find boxart. (404)
19:40:09 - Searching art for Assassins Creed 2 - Discovery (EU).nds..
19:40:12 - Got it!
19:40:12 - Searching art for Asterix - These Romans Are Crazy! (EU).nds..
19:40:16 - Got it!
19:40:16 - Searching art for Atari Greatest Hits - Volume 1 (EU).nds..
19:40:18 - Got it!
19:40:18 - Searching art for Avalon Code (EU).nds..
19:40:26 - Got it!
19:40:26 - Searching art for Bakugan - Battle Brawlers (EU).nds..
19:40:33 - Got it!
19:40:33 - Searching art for Barbie - Groom and Glam Pups (EU).nds..
19:40:36 - Got it!
19:40:36 - Searching art for Barbie and the Three Musketeers (EU).nds..
19:40:41 - Got it!
19:40:41 - Searching art for Ben 10 - Triple Pack (EU).nds..
19:40:45 - Got it!
19:40:45 - Stopped by user.
19:40:45 - Finished scan.
Result in the image.