Sounds like a case of stale proxy cache to me.
Surely a stale cache would result in an incorrect download, not a hanging one?
What are you using to download it? Have you tried wget and/or curl on your Linux system? What does HEAD (a perl script) show for it? I get:
[mysys]: HEAD
http://www.plugcomputer.org/guruplug/rfs/rootfs.ubi.img200 OK
Connection: close
Date: Wed, 16 Jun 2010 21:56:47 GMT
Accept-Ranges: bytes
ETag: "10e3e2-b940000-cbcbc280"
Server: Apache/2.0.63 (Unix) mod_ssl/2.0.63 OpenSSL/0.9.8b mod_auth_passthrough/2.1 mod_bwlimited/1.4 FrontPage/5.0.2.2635 PHP/5.2.8
Content-Length: 194248704
Content-Type: application/x-img
Last-Modified: Mon, 10 May 2010 17:32:42 GMT
Client-Date: Wed, 16 Jun 2010 21:56:47 GMT
Client-Peer: 97.74.126.48:80
Client-Response-Num: 1