The situation is much better now, but not perfect.
All the themes work, and the "The Look" setup page works, provided I delete the folder night (Night Theme)!
If I keep the folder night there, not only the Night Theme does not work, but the same previous error occurs : I cannot get the /setup/5 page and change any theme.
If I delete the folder night, everything works fine, I can access the /setup/5 page and change the theme (chosen any from the other original ones).
So, I thought that there was an error in the current Night Theme files, and I downloaded the 4 original files of the folder night fromhttp://pkp.sfu.ca/cvs/cvsweb.cgi/ojs2/p ... =c#dirlist
and uploaded to the journal website.
Result: the same!
If the folder night is there, the "The Look" setup does not work. If I delete night, everything works fine.
The permission codes are the same as the working themes. Also, I can browse the night files and see no error.
In simple words, I have lost just one theme (night): not a big damage. However, if someone can suggest how to recover it, it would be perfect.