Help me with Webrick [BUG] rb_sys_fail()

Hello,

The Webrick based program I have dies with this message:
/usr/lib/ruby/1.8/webrick/httprequest.rb:307: [BUG] rb_sys_fail() - errno == 0 ruby 1.8.2 (2004-08-24) [i386-linux]

It is running on debian testing.

I think the error occurs when one person (who is running IE6 in Win XP SP2) gets redirected from the server (part of the logout process) and then quits their browser. Other people seem not to trigger the bug, but it is repeatable with this guy.

Could anybody give me any clues as to what I might need to fix?

Many thanks

Tom