CGI temp file lock?

I am using attachment_fu. During uploads - it creates (I think its
attachment_fu or is it apache?) a tmp file as /tmp/CGI-xxxxxx.
On some occasion, I noticed that this file is not closed and hence
the ruby instance resource is never released.
Any one have any insights on this?

(I am on Fedora 8, rails 1.8, apache2)