export snapshot only runs once

[Shao Sean]

I looked over the list archive as well as Bugzilla and only found  
information related to a memory leak.
When I run the following code:

   export snapshot from player "hello" to tPig as JPEG

it works the first time, but the second time I get the following error:

   (export: can't write to file, mask file, or container), char 1

I get the error regardless of exporting to a container (tPig) or to a  
file.
Am I doing something wrong? Is there an easier way to export a screen  
capture of a single frame from a player object?