qemu-img convert hexdump of working and non

the disk qemu-img converts (this is not a bootable disk, but qemu-img converted many bootable ones too):

peter:/mnt # hexdump -C /mnt/bcnasvm1/bcvm01-00/bcvm01-00_1-000001-flat.vmdk | head -n25
00000000  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
000001b0  00 00 00 00 00 00 00 00  d2 7a c1 e0 00 00 00 01  |.........z......|
000001c0  01 00 8e fe ff ff 3f 00  00 00 59 e0 7f 07 00 00  |......?...Y.....|
000001d0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
000001f0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 55 aa  |..............U.|
00000200  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
00008000  4c 41 42 45 4c 4f 4e 45  01 00 00 00 00 00 00 00  |LABELONE........|
00008010  b3 1f a4 fd 20 00 00 00  4c 56 4d 32 20 30 30 31  |.... ...LVM2 001|
00008020  79 53 52 4a 56 6d 71 65  52 4e 6d 4b 50 62 4d 63  |ySRJVmqeRNmKPbMc|
00008030  69 6e 7a 4e 59 46 30 79  52 70 43 45 65 4c 4c 74  |inzNYF0yRpCEeLLt|
00008040  00 b2 c0 ff 0e 00 00 00  00 00 03 00 00 00 00 00  |................|
00008050  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00008060  00 00 00 00 00 00 00 00  00 10 00 00 00 00 00 00  |................|
00008070  00 f0 02 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00008080  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
00008e00  83 c5 37 8e 20 4c 56 4d  32 20 78 5b 35 41 25 72  |..7. LVM2 x[5A%r|
00008e10  30 4e 2a 3e 01 00 00 00  00 10 00 00 00 00 00 00  |0N*>............|
00008e20  00 f0 02 00 00 00 00 00  00 06 00 00 00 00 00 00  |................|
00008e30  a4 03 00 00 00 00 00 00  16 f6 a2 27 00 00 00 00  |...........'....|
00008e40  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|


The disk qemu-img won't convert:

peter:/mnt # hexdump -C /mnt/bcnasvm1/bcvm01-18/bcvm01-18-flat.vmdk | head -n 25
00000000  eb 63 90 d0 bc 00 7c fb  50 07 50 1f fc be 1b 7c  |.c....|.P.P....||
00000010  bf 1b 06 50 57 b9 e5 01  f3 a4 cb bd be 07 b1 04  |...PW...........|
00000020  38 6e 00 7c 09 75 13 83  c5 10 e2 f4 cd 18 8b f5  |8n.|.u..........|
00000030  83 c6 10 49 74 19 38 2c  74 f6 a0 b5 07 b4 07 8b  |...It.8,t.......|
00000040  f0 ac 3c 00 74 fc bb 07  00 b4 0e cd 10 eb f2 88  |..<.t...........|
00000050  4e 10 e8 46 00 73 2a fe  46 10 00 80 01 00 00 00  |N..F.s*.F.......|
00000060  00 00 00 00 ff fa 90 90  f6 c2 80 75 02 b2 80 ea  |...........u....|
00000070  74 7c 00 00 31 c0 8e d8  8e d0 bc 00 20 fb a0 64  |t|..1....... ..d|
00000080  7c 3c ff 74 02 88 c2 52  bb 17 04 80 27 03 74 06  ||<.t...R....'.t.|
00000090  be 88 7d e8 1c 01 be 05  7c f6 c2 80 74 48 b4 41  |..}.....|...tH.A|
000000a0  bb aa 55 cd 13 5a 52 72  3d 81 fb 55 aa 75 37 83  |..U..ZRr=..U.u7.|
000000b0  e1 01 74 32 31 c0 89 44  04 40 88 44 ff 89 44 02  |..t21..D.@.D..D.|
000000c0  c7 04 10 00 66 8b 1e 5c  7c 66 89 5c 08 66 8b 1e  |....f..\|f.\.f..|
000000d0  60 7c 66 89 5c 0c c7 44  06 00 70 b4 42 cd 13 72  |`|f.\..D..p.B..r|
000000e0  05 bb 00 70 eb 76 b4 08  cd 13 73 0d f6 c2 80 0f  |...p.v....s.....|
000000f0  84 d0 00 be 93 7d e9 82  00 66 0f b6 c6 88 64 ff  |.....}...f....d.|
00000100  40 66 89 44 04 0f b6 d1  c1 e2 02 88 e8 88 f4 40  |@f.D...........@|
00000110  89 44 08 0f b6 c2 c0 e8  02 66 89 04 66 a1 60 7c  |.D.......f..f.`||
00000120  66 09 c0 75 4e 66 a1 5c  7c 66 31 d2 66 f7 34 88  |f..uNf.\|f1.f.4.|
00000130  d1 31 d2 66 f7 74 04 3b  44 08 7d 37 fe c1 88 c5  |.1.f.t.;D.}7....|
00000140  30 c0 c1 e8 02 08 c1 88  d0 5a 88 c6 bb 00 70 8e  |0........Z....p.|
00000150  c3 31 db b8 01 02 cd 13  72 1e 8c c3 60 1e b9 00  |.1......r...`...|
00000160  01 8e db 31 f6 bf 00 80  8e c6 fc f3 a5 1f 61 ff  |...1..........a.|
00000170  26 5a 7c be 8e 7d eb 03  be 9d 7d e8 34 00 be a2  |&Z|..}....}.4...|
00000180  7d e8 2e 00 cd 18 eb fe  47 52 55 42 20 00 47 65  |}.......GRUB .Ge|