apt-get update
Get:1 http://ftp.us.debian.org sid Release.gpg [189B]
Hit http://ftp.us.debian.org sid Release
Get:2 http://ftp.us.debian.org sid/main Packages [4578kB]
99% [2 Packages bzip2 2699264]
bzip2: Data integrity error when decompressing.
        Input file = (stdin), output file = (stdout)

It is possible that the compressed file(s) have become corrupted.
You can use the -tvv option to test integrity of such files.

You can use the `bzip2recover' program to attempt to recover
data from undamaged sections of corrupted files.

Err http://ftp.us.debian.org sid/main Packages
  Sub-process bzip2 returned an error code (2)
Fetched 2B in 2s (1B/s)
Failed to fetch http://ftp.us.debian.org/debian/dists/sid/main/binary-amd64/Packages.bz2  Sub-process bzip2 returned an error code (2)
Reading package lists... Done
W: Couldn't stat source package list http://ftp.us.debian.org sid/main Packages (/var/lib/apt/lists/ftp.us.debian.org_debian_dists_sid_main_binary-amd64_Packages) - stat (2 No such file or directory)
W: Couldn't stat source package list http://ftp.us.debian.org sid/main Packages (/var/lib/apt/lists/ftp.us.debian.org_debian_dists_sid_main_binary-amd64_Packages) - stat (2 No such file or directory)
W: You may want to run apt-get update to correct these problems
E: Some index files failed to download, they have been ignored, or old ones used instead.