It sounds as though the magnet must be mwerneck's problem. For the sake of anyone else with strange internal-card behaviour after a fall, there is something else to look for. The slider that holds the card in place can move. Make sure that it is pushed all the way in the direction of the arrow.

Like mwerneck, I had no problem booting from the second partition of the internal card after dropping the N800. I have swap ("virtual memory") on a third partition of the internal card, and I don't know whether it was still active or not after the fall. In my case, the N800's strange behaviour was that the browser and Media Player would not save new bookmarks. The N800 said they were saved, but then they were not there when I looked for them.

To fix the problem, I tried to restore a backup, but got a message saying that the backup was not available. That suggested the internal card as a possible cause. I looked inside and found that the slider was all the way in the "out" position. After sliding it back in, everything worked again.