Interbase: I/O error for file KATALOG.GDB - Error while trying to read from file

Problem:

I use Delphi 2.0 (C/S Suite) and the local interbase server. My
application use a database KATALOG.GDB stored on the local harddisk.
Filesize is about 1,1MB. After a reboot I'm not able to connect to the
database file. After the login to the server (SYSDBA, MASTERKEY) I try
to connect to the database with the following result:

   I/O error for file "D:\KATALOG.GDB"
   - Error while trying to read from file
   - Der Vorgang wurde ausgefuehrt

I tried to repair the database with GFIX.EXE (interbase\bin directory)
with the same result. I tried the "-ignore" switch (to ignore the
checksum of the database) - no result.

I need the access to this database! What's the way to repair it? Perhaps
a combination of switchs or calls with the GFIX program?

/Stefan