Problem with apt-get update

[Adam Membrey]

I've been trying to do a sudo apt-get update for the past 12 hours and I'm 
constantly getting:

Get:3 http://archive.ubuntu.com hoary/main Packages [632kB]
99% [3 Packages gzip 0] [Waiting for headers]
gzip: stdin: not in gzip format
Err http://archive.ubuntu.com hoary/main Packages
  Sub-process gzip returned an error code (1)

doing a sudo tcpdump -lvv |grep ubuntu gives the following:

09:06:52.926855 IP (tos 0x0, ttl  64, id 65174, offset 0, flags [DF], length: 
64) 192.168.0.6.35070 > dns.meb.optusnet.com.au.domain: [bad udp cksum cdc3!]  
11535+ A? archive.ubuntu.com. (36)


Anyone able to suggest how to go about fixing this ?

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