just a short notice to say that I just solved the problem thanks to this post. i was unable to have write acess to my fat32 memory on the nokia n900 with the same error messages posted above for taking pictures and saving files to disk.

I do not use windows but the fix on linux is similar: plug in your n900, run your disc utility tool, go to the 32Gb fat32 drive unmount it and click the button that says check and repair. I got a message after less than a minute saying that there was no problem. And viola! phone back to it's usual self.

BTW my original username is andresm but i have closed the email attached to that user name. Sorry!