When at the tar step, I had no problem with a 2GB Kingston RS-MMC. When I try on a 4GB Transcend SD card, tar always stalls at a random point and I have brutely to reboot (extract battery). This won't likely be healthy for my device. Any hint?

EDIT: the last time I tried, it bricked by n800 and had to reflash

SOLVED: for some strange reason it has been necessary to avoid verbose output of the tar extracting part, so it works with "tar xf" instead of "tar xvf".