Yes, the file exists and has read permission.
The problems are two:
1.- 'RestrictErrorsToAdminsP' in kernel config set to '1'
Problem: When a query fails, whatever the reason, all the users can see the debug error. For example: 'db_0or1row' failed to... etc.
In the same server i have some other openacs working fine. When a error appears only the admins can see it. The normal users cant see it. They receive a generic programming error 'we are investigating it', etc .
2.- I think it can be related with the first one: When i set a error page, the system cant reach it, whatever the name i set, whatever the route to the file. Openacs always shows the system error problem.