This error is caused by a malfunction in the inter-process pipe (stream) opened in the OS by the web server.
When this bug manifests, the last data blocks are not flushed in the stream, so Picture to People code (CGI) never gets all request data, so a time-out error happens.
It is not an error on Picture to People code, and we can not solve or avoid it. Fortunately this error happens very rarely.
Try to crop or to stretch the input image a little and possibly it may work.