PITR WAL Archive error on idle database

Hi,

I am new to Postgres and installed postgres 8.3.7 build 1200 Windows 2003
server .

I have implemented PITR with WAL shipping which takes one full backup and an
hourly backup of the WAL files through backup scripts.The backup script is
just copying the files after pg_switch_xlog().

On Saturday of last week, backups started to fail and following error was
throw in the logs:

2009-08-28 23:26:55.357 EDT,5648,LOG: archive command failed with exit code
1

2009-08-28 23:26:55.357 EDT,5648,DETAIL: The failed archive command was:
call "E:\Entrust\Security Manager\bin\ARCHWAL.BAT"
"pg_xlog\0000000100000003000000E2"

*The DB was in an idle state and no activities were being performed on it
when the issue appeared. *

Later on with some analysis, I checked there was a file with same name in
archive_status directory but with .ready, so I renamed that file and it
looks the problem got resolved,but after an hour when backup script ran
again it throws similar error but with different name.

postgresql1.log:2009-08-31 17:41:35.117 EDT,5648,WARNING: transaction log
file "000000010000000400000010" could not be archived: too many failures

postgresql1.log:2009-08-31 17:42:37.226 EDT,5648,WARNING: transaction log
file "000000010000000400000010" could not be archived: too many failures

All the parameters in postgresql.conf are default.

Can I know the reason as why it is happening and how can I resolve it.

Regards
Abhishek