Elasticsearch Writes Into S3 Bucket for Metadata But Doesn't Write Into S3 Bucket For Scheduled Snapshots Problem

According to the documents at
I have included the respective API Access Key ID with its secret access key
and Elasticsearch is able to write into the S3 bucket as follows:

[2012-08-02 04:21:38,793][DEBUG][gateway.s3] [Schultz, Herman] writing to gateway org.elasticsearch.gateway.shared.SharedStorageGateway$2@4e64f6fe ...
[2012-08-02 04:21:39,337][DEBUG][gateway.s3] [Schultz, Herman] wrote to gateway org.elasticsearch.gateway.shared.SharedStorageGateway$2@4e64f6fe, took 543ms

However when it comes to writing snapshots into the S3 bucket, out comes
the following error:

[2012-08-02 04:25:37,303][WARN ][index.gateway.s3] [Schultz, Herman] [plumbline_2012.08.02][3] failed to read commit point [commit-i] java.io.IOException: Failed to get [commit-i]
Caused by: Status Code: 403, AWS Service: Amazon S3, AWS Request ID: E084E2ED1E68E710, AWS Error Code: InvalidAccessKeyId, AWS Error Message: The AWS Access Key Id you provided does not exist in our records.
[2012-08-02 04:36:06,696][WARN ][index.gateway] [Schultz, Herman] [plumbline_2012.08.02][0] failed to snapshot (scheduled) org.elasticsearch.index.gateway.IndexShardGatewaySnapshotFailedException: [plumbline_2012.08.02][0] Failed to perform snapshot (index files)

Is there a reason why this is happening since the access keys I have
provided is able to write metadata and not creating snapshots?