Oracle7.3 ODBC

My Delphi Pro 4.03/BDE 5.10 program can connect to Oracle7.3 via ODBC at
design time, but not at run time! I use a TTable, TDataSource and TDBGrid
and can access an Oracle table at design time, but I get ORA-00000 when I
run the application. I've tried both MS for Oracle and Oracle's ODBC
drivers, which both work OK for MS Access97. Others have had this problem
too, but I can't find a solution. Borland says it isn't a BDE bug.
Can you help?