Can anyone id this pretty white flower which appeared in the yard of
the vacant house next door for one day and then quickly faded (very
ephemeral). Appeared May 12, 2009, in Northeast Ohio. Blooms were up
to 1 1/2" across and the whole plant was only several inches high.

Links to flower pictures:
http://www.flickr.com/photos/cpal/3558210135/
http://www.flickr.com/photos/cpal/3559021282/
http://www.flickr.com/photos/cpal/3559022338/
http://www.flickr.com/photos/cpal/3558213437/