> so you're suggesting he's been modifying the firebird.conf file and hasn't
> told us what changes he's tried making...

It is one of possibilities, but current dir is more probably because
he uses isql. Look at this:

C:\... Files\Firebird\Firebird_2_1\bin>isql.exe -u sysdba -pass
masterkey testa
Statement failed, SQLCODE = -902
I/O error for file "C:\PROGRAM FILES\FIREBIRD\FIREBIRD_2_1\BIN\TESTA"
-Error while trying to open file
-The system cannot find the file specified.

C:\... Files\Firebird\Firebird_2_1\bin>isql.exe -u sysdba -pass
masterkey test
Database: test, User: sysdba

I do have alias "test".

SY, SD.