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

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