Atom Issue with different Twitter accounts

I'm using an atom feed parsed via PHP to display the most recent post.

The URL that feeds into this is: http://search.twitter.com/search.atom?q=from:username&rpp=1.

When using username=nickpricedesign, it generates a valid feed, whereas using username=landformstudios doe开发者_运维百科s not.

Please could somebody assist me as to why the atom feed is not displayed correctly with one account, yet is fine with the other?

Thanks, Nick

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The problem is that the tweets of landformstudios are too old. If you post a new tweet it will return the latest tweet.