Presuming that this is still an issue... have you taken a look at ddrescue?
http://www.gnu.org/software/ddrescue/ddrescue.html

I use it to clone hard drives as part of my backup strategy for my laptop. It's wonderfully effective. I've no idea if anyone's even thought about compiling it for Maemo, let alone done so (I wouldn't be able to - I take one look at the Scratchbox installation docs and go into twitching fits), but it ought to help.