Yes, you can use mkfs.jffs2 also on linux desktop to create the image later. Linux/Mac flasher can write such image of rootfs (or initfs or kernel) separately.
Sadly it cannot read it from device.
Could be faulty hardware or you may be victim of this http://blog.homac.de/?p=58 a.k.a Power up Drama http://bugs.maemo.org/show_bug.cgi?id=2673