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.