qemu-img fails to convert image

On a Windows XP system and an NTFS drive, using QEMU on Windows Ver 0.12.2 from http://homepage3.nifty.com/takeda-toshiya/qemu/ or QEMU 0.12.3 built locally, when I run the following commands, a dialog is displayed indicating that "qemu-img.exe has encountered a problem and needs to close".

 qemu-img create foo.img 1G
 qemu-img convert -O qcow2 foo.img bar.img