Parted Magic doesn't work in system "Backup" plugin

[My system basic info]:
================================================================================
= OS/Debian information
================================================================================
Distributor ID: debian
Description: Debian GNU/Linux 7 (wheezy)
Release: 7.6
Codename: wheezy
Kernel: 3.14 backport
================================================================================
= OpenMediaVault information
================================================================================
Release: 1.0.8
Codename: Kralizec

Gparted iso: gparted-live-0.19.1-1-amd64.iso
Backup plugin: openmediavault-backup 1.0.4

[Issue symptom]:
After installing "backup" plugin, I continued to setup "Parted Magic" as guided in the tab, copied iso file to /boot/ and automatically updated the grub loader, then clicked "Parted Magic" button to setup one-time boot, but after reboot the system, couldn't load the iso, error message looks as: error, can't find the file.

My grub menu for Gparted is as below, and I can confirm the iso exist there.
### BEGIN /etc/grub.d/42_partedmagic ###
menuentry "Parted Magic" {
set isofile="/boot/partedmagic.iso"
loopback loop $isofile
linux (loop)/pmagic/bzImage iso_filename=$isofile boot=live
initrd (loop)/pmagic/initrd.img
}
### END /etc/grub.d/42_partedmagic ###

Note: I tried to burn iso to a USB disk using UltraISO, booting also failed, because the loader in iso is syslinux v4, but UltraISO can't write correctly, so I changed to another tool -- "rufus-1.4.5.exe", i downloaded a file from the net when writing the iso, after that, this USB disk worked well to log in Gparted UI, so i'm wondering whether this issue is that grub loader in Debian Wheezy can't recognize iso correctly.

yes, i configured the share folder to put iso, as below, the iso under /boot/ is copied by installation script.

This is the screenshot when booted with Gparted:

As it was at very early stage of booting, so I'm wondering it has any relationship with OMV network setting, dhcp or static, also my eth0 did set to dhcp.
This is my OMV setup on baremetal system, a HP ProLiant SL210t Gen8, but I also had the same issue on my home system, DIYed NAS.

Sorry for my newbie head, I thought they are the same one, I will try the correct iso.

BTW, is partedmagic a totally open source tool, as I found it requires $4.99 for iso download and one year subscription.