Flickr API returning a result set with hits but an empty photo array.

Question

I am making a Flickr api call to flickr.photos.search to find all the photos near a certain lat/lon. It works just for the normal case, but I have found that if I add a text search term to the search I sometimes get a strange return result from Flickr:

jsonFlickrApi({"photos":{"page":1, "pages":5, "perpage":250, "total":"1153", "photo":[]}, "stat":"ok"})

You can see from the returned JSON string that there are hits for my search but the photo array is empty. (The info for the first page of photos is supposed to be in that photo array.) I don't get the problem for every search, so if I change the text portion of the search to a different string, it might work fine. For any give search text where it gives the 'bad' result, it seems to happen every time. Here is an example URL that generates the problem for me:

http://api.flickr.com/services/rest/?method=flickr.photos.search&media=photos&sort=interestingness-desc&min_taken_date=2005-01-01%2000%3A00%3A46&extras=geo%2C%20date_taken&format=json&lat=28.4&lon=-81.6&radius=3&text=pirate&api_key=XXXXXXXXXXXXXXXXXXXX&api_sig=7dfb4c01d8a4734bbdf2e464867d65bf

Any ideas what might be going on here?