When getting the above error then open up a command prompt.
type,
c:\program files\firebird\firebird_1_5\bin\ * add (x86) if necessary.
gsec -database 127.0.0.1: "c:\program files\firebird\firebird_1_5\security.fdb" -user SYSDBA -password masterkey
then type,
add AMETHYST -pw password
This is not the correct password ^^^^
ignore warning and type quit.