SQL*Loader Error

Hi,
I can login properly using sql*plus, but when I invoke sql*loader I get this below error.How to resolve this issue. (I am not dba)



SQL*Loader: Release 7.3.4.0.0 - Production on Thu Jun 05 15:49:39 2003

Copyright (c) Oracle Corporation 1979, 1996. All rights reserved.

SQL*Loader-925: Error while logging on to ORACLE (ulmconnect)
ORA-12154: TNS:could not resolve service name


Run began on Thu Jun 05 15:49:39 2003
Run ended on Thu Jun 05 15:49:40 2003

Elapsed time was: 00:00:00.50
CPU time was: 00:00:00.00 (May not include ORACLE CPU time)

Do you have multiple Oracle Home or Multiple tnsnames.ora on the machine you are runnind SQL*Loader ?