Comment 11 for bug 1172065

Oddly, the filename appears fine when the iso is mounted under linux:

$ sudo mount -o ro -t iso9660 ubuntu-12.04.3-desktop-amd64.iso /mnt
$ ls -l /mnt/pool/main/g/grub2-signed/
total 479
-r--r--r-- 1 root root 489626 Jul 22 16:43 grub-efi-amd64-signed_1.9~ubuntu12.04.4+1.99-21ubuntu3.10_amd64.deb

But the last two characters before the extension are dropped when the iso is mounted under windows:

F:\>dir \pool\main\g\grub2-signed
 Volume in drive F is Ubuntu 12.04.3 L
 Volume Serial Number is 8BB6-BA54

 Directory of F:\pool\main\g\grub2-signed

2013/08/20 20:08 <DIR> .
2013/08/20 20:08 <DIR> ..
2013/07/22 16:43 489 626 grub-efi-amd64-signed_1.9~ubuntu12.04.4+1.99-21ubuntu3.10_amd.deb
               1 File(s) 489 626 bytes
               2 Dir(s) 0 bytes free

A difference in iso filesystems perhaps?
Someone with knowledge of iso should probably look at this.