The issue was reported by Ivan C Cruz:

I have start testing Firebird 2.1 last week and stumbled in a possible bug:
whenever I select from one of the new monitoring virtual tables I receive
the error:

Statement failed, SQLCODE = -902
operating system directive open failed
-Permission denied

In isql, the error is printed just after the headers. No records are
printed.
In the firebird.log I get this:

IvanAMD32 (Server) Tue Feb 5 23:52:36 2008
    Cannot initialize the shared memory region

Tested with both beta(?) 2 and rc 1. OS is Ubuntu 7.10. Firebird is
SuperServer 2.1.0.17735 installed with the script provided in
the tar.gz package. Database was backed up and restored
properly. ODS version is 11.1. Problem only happens with
monitoring tables and everything else looks OK.