When you flash both emmc and rootfs the system hangs a lot of time on first boot due to optification of the file system - up to several minutes (sincerely I don't know on which basis but it's mentioned somewhere in the docs).
This happened once to me, when I fear to have lost my beloved 900. My suggestion is to try the following procedure as per Wiki:
- start with a fresh battery
- flash the eMMC without rebooting
- flash the fiasco image
- reboot and see the 5 dot blinking
- go to bed and wait until tomorrow before looking at your n900 again

Once it happened to me the dots blinked for half an hour, perhaps more. I repeat that I don't know why it took so long to optify the system while usually it does not take more than a couple of minutes, but it happened. My little beast still works.