SQL & PL/SQL

Hi.
We are using database 10g for data warehousing which is on unix server.

Yesterday and the time before that we was able to do any of select from all external tables that we have in database, but suddenly from today we can't select any of our external tables. I don't know where is an error. I though that error might be that database can't see directory but this is not error because directory exists and all files for all external tables are there. What else might be wrong? Is something with oracle_loader, or unix?

This is my log where I try to select external table:

ORA-29913: error in executing ODCIEXTTABLEOPEN callout
ORA-29400: data cartridge error
KUP-04063: unable to open log file dw_sources.log
OS error No such file or directory
ORA-06512: at "SYS.ORACLE_LOADER", line 19

This error appear 2 times for each external table.

This is script mentioned ext. table above

CREATE TABLE EXT_DWH_SOURCES
(
DWH_SOURCE_CODE VARCHAR2(10 BYTE),
DWH_SOURCE_NAME VARCHAR2(100 BYTE)
)
ORGANIZATION EXTERNAL
( TYPE ORACLE_LOADER
DEFAULT DIRECTORY FILES_DIR
ACCESS PARAMETERS
( RECORDS DELIMITED BY NEWLINE
CHARACTERSET EE8MSWIN1250
STRING SIZES ARE IN BYTES
BADFILE BAD_FILES_DIR:'dwh_sources.bad'
DISCARDFILE DSC_FILES_DIR:'dwh_sources.dsc'
LOGFILE LOG_FILES_DIR:'dwh_sources.log'
FIELDS
LRTRIM
MISSING FIELD VALUES ARE NULL
(
"DWH_SOURCE_CODE" POSITION (1:2) CHAR,
"DWH_SOURCE_NAME" POSITION (3:52) CHAR
)
)
LOCATION (FILES_DIR:'dwh_sources.txt')
)
REJECT LIMIT UNLIMITED
NOPARALLEL
NOMONITORING;

I can connect through FTP to any of files directory on Unix so files are there!

Where is the problem?

Thanks for help.

Deep