The dd command had failed, but the command runs fine on my N900 Try the command please without the conv=noerror part.
BusyBox v1.10.2 (Debian 3:1.10.2.legal-1osso30+0m5) built-in shell (ash) Enter 'help' for a list of built-in commands. ~ $ sudo gainroot Root shell enabled BusyBox v1.10.2 (Debian 3:1.10.2.legal-1osso30+0m5) built-in shell (ash) Enter 'help' for a list of built-in commands. /home/user # dd if=/dev/zero of=/dev/mmcblk0 seek=44400704 count=16777216 bs=512