Here is the test I did with the NB-656 using the DivX Test CD 2.0:
MPEG4 ASP (XviD, DivX 4, DivX 5, DivX 6, 3ivX, Nero Digital ASP…)
Vid 3A – MPEG4 ASP 4CC DivX + MP3 CBR (simple DivX codec compatibility test) = YES
Vid 3B – MPEG4 ASP 4CC XviD + MP3 CBR (simple XviD codec compatibility test) = YES
Vid 3C – MPEG4 ASP Bframes + MP3 CBR (multi Bframe without packet bitstream compatibility test) = YES, Number of bitstream supported is 3 (out of maximum 3)
Vid 3D – MPEG4 ASP Bframes pack and bitstream + MP3 CBR CBR (multi Bframe with packet bitstream compatibility teats) = YES, Number of bitstream supported is 3 (out of maximum 3)
Vid 3E – MPEG 4 ASP Custom Matrix + MP3 CBR (Custom matric compatibility test) = YES
Vid 3F – MPEG 4 ASP Qpel + MP3 CBR (Qpel compatibility test) = YES
Vid 3G – MPEG 4 ASP GMC 1 WP & 3 WP + MP3 CBR (GMC 1 & 3 Warp Point) (DivX and XviD compatibility test) = YES, with 3 Warp Points
Vid 3H – MPEG 4 ASP Bitrate Crash Test + MP3 CBR 750/1500/3000/4500 (crash test with 4 levels of complexity)= YES, Supported bitrate is 4500
Vid 3I – MPEG 4 ASP High Definition 1280*720 (HD720p compatibility test) = NO, but with audio
Vid 3J – MPEG 4 ASP High Definition 1920*1088 (HD1080p compatibility test) = NO, no but with audio
I also had a problem playing a MP4 before but it turned out that the file has 720p resolution which my TV cannot play ( but there is audio), as shown in the test results above.
As to your problem, better burn the file again on another medium or DVD-R/CD-R brand. And most importantly do not remove the .avi extension file in your file when you burn it/them. I did it once before and it won't play in the 656.
Better yet, can you give the site where you downloaded said MP4 file. Ida-download ko and i will test it on my player. If it plays, then maybe there's really a problem either with your media or your player.