Hello! I had the same problem and I reflash bouth partitions and works.

First go to:

https://wiki.maemo.org/Updating_the_firmware

Download the firmware (RX-51_2009SE_2.2009.51-1_PR_COMBINED_MR0_ARM.bin) and the eMMC VANILLA one (note that you have to install the old version - RX-51_2009SE_1.2009.41-1.VANILLA_PR_EMMC_MR0_ARM.bin).

Install the eMMC first and then the last combined firmware later.

Enjoy!
Pd: Don't forget to backup previusly... this will leave your N900 like out of the box