Goldengate Error 500

Greetings:

I've setup goldengate, but my extracts is returning with the following error?  Why?

2010-08-10 18:12:01  GGS ERROR       500  Could not find archived log for sequence 0 thread 1 under default destinations SQL <SELECT  name    FROM v$archived_log   WHERE sequence# = :ora_seq_no AND         thread# = :ora_thread AND         resetlogs_id = :ora_resetlog_id AND         archived = 'YES' AND         deleted = 'NO>, error retrieving redo file name for sequence 0, archived = 1, use_alternate = 0Not able to establish initial position for begin time 2010-08-10 17:36:20.

2010-08-10 18:12:01  GGS ERROR       190  PROCESS ABENDING.