Intermittent buffering

Hello, I am working on a channel and I am having loading issues with my videos. The videos load and play, but it takes a while and they buffer every 2-3 minutes. I am using Amazon S3/Cloudfront and my internet speed is at 11 Mbps.
I am using this guide to encode my videos. http://sdkdocs.roku.com/display/sdkdoc/Encoding+Guide
Any ideas as to why it is not working correctly?