this is a complex question because it deals with WinXP, VirtualBox, Ubuntu and a specific Windows executable.
So I have a program (SilkyPix, a RAW image processor) that runs in a VirtualBox session on my Ubuntu machine. It used to run fine, but the last (expensive) upgrade now has problems: it works fine on local RAW files, but it fails when the files are on a VirtualBox shared folder. It's like the program cannot create its destination files there.
It used to run fine, so the permissions should be OK, and I can create files there with Windows without problem. Other Windows programs have no problems... Well, now that I think about it, one other program, an IDE editor, also has problems.
$ ll -d / /Ter /Ter/Large1 /Ter/Large1/Pictures /Ter/Large1/Pictures/2012 /Ter/Large1/Pictures/2012/2012070*
drwxr-xr-x 28 root root 4096 Jul 1 18:14 //
drwxr-xr-x 11 root root 4096 Feb 13 19:41 /Ter/
drwxrwxr-x 21 dargaud dargaud 4096 Mar 17 19:52 /Ter/Large1/
drwxrwxr-x 25 dargaud dargaud 4096 Jan 15 15:56 /Ter/Large1/Pictures/
drwxrwxr-x 61 dargaud dargaud 36864 Jul 8 19:52 /Ter/Large1/Pictures/2012/
drwxrwxr-x 3 dargaud dargaud 57344 Jul 10 00:03 /Ter/Large1/Pictures/2012/20120707_MG40_AnneesFolles/
drwxrwxr-x 4 dargaud dargaud 36864 Jul 9 23:57 /Ter/Large1/Pictures/2012/20120707_MG40_Riviere/
drwxrwxr-x 3 dargaud dargaud 20480 Jul 10 12:07 /Ter/Large1/Pictures/2012/20120708_MG40_Matin/
$ grep vb /etc/passwd /etc/group