But maybe you anything if you know how to flashing the N900 with Windows 8? Because does not cope, maybe rewrote everything becomes good.

Flashing with Windows 8 is like flashing with every other Windows version. I run Win8 X86 and could do it the first time without any problems, just follow the wiki!

Also install Nokia PC Suite, latest version, go to software updates and click on Reinstall FW (this is the easy method).

Flashing sounds like an overkill. The most likely causes are:
1) The camera app is set to save the pictures to an SD card but no SD card is present;
2) There are problems with the partition (either internal or SD, the same thing applies) and it was mounted as read only. This might happen if it wasn't ejected properly. Try confirming by creating/renaming/deleting a test file in the target folder.

If #2 is your problem, the simple solution is to connect the phone to your Windows PC in mass storage mode, run chkdisk on it and then eject it cleanly. If that doesn't help then, with the phone disconnected from PC, open the terminal on the phone and type these two commands:
and post the output.