did you flash the EMMC 1st? considering the fact that your N900 doesn't boot up anymore, this may not matter, alas. that's where it would be handy to have a +real+ backup / restore tool (i.e. partimage) that would allow you to start Rescue OS, indeed, and either use earlier images (both of / and /opt) of your own functioning device or, at default, from any other working N900