The message error usually means that the information in your configuration file is obsolete.
If that does not suffice, restart SCID. If that still does not work, it could be because your configuration file needs to be replaced.
SCID stores personal settings inside a directory.
Under Win, it's called /YourScidInstallation/bin/config
Simply delete the directory and its files. 
Under Linux and OSX, it's called ".scid".
If you open a terminal on your home directory and type:
grep -iRn books .scid
You should see where SCID is searching for the books directory.
Simply delete the directory and its files. 
(You can move it elsewhere if you wish to keep it.)
SCID will then restart with the default settings.
It will also recreate the .scid directory, as you save your options.