Problem in downloading large file(1.1 gb) using xsendfile mo

Hi all,
I am Running Apache as frontend server to mongrel and uploaded 1.1 Gb
of file using my rails application .Now I am trying to download same 1.1
GB stream ,for that i loaded in apache httpd.conf file
and using send_file function downloaded this 1.1 gb of stream
successfully.but after downloading it ,again am trying to download same
1.1 gb of stream but now am getting failed to allocate memory error.
what is the problem??