Large HTTP downloads

I have just got our squiddly-diddly up and running and have a problem
that I can't see how to fix. Everything's fine except for large file
downloads (>1M or so) using http. They gradually get slower, then time
out after between 500k and 2M. Going around the caching, proxy squid
server and straight to the firewall, the files come in fine so it's
definitely something to do with the squid proxy.

Any ideas?

-- 
^~^~^~^~^~^~^^~^~^~^~^~^~^~^~^~^~^~^~~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~
	 Martin Brown, UNIX Systems and Network Administrator
   ADI Ltd, Systems Group, Private Bag 2, Nth Ryde 2113, Australia
Phone: +61 2 9325 1645  Fax: 9325 1600  Email: martin.brown@sg.adisys.com.au