I had some unknown issues with the archive script that caused me to lose a lot of data. It turned out to be because my key/secret credentials are scoped to one bucket. PHP-S3 tried to connect to aws and failed.
The fix was to change the ACL flag from public to private:
S3:ACL_PUBLIC_READ
to
S3::ACL_PRIVATE
https://code.google.com/p/webpagetest/source/browse/trunk/www/webpagetest/archive.inc#95