Kind of an odd issue.  Ran:

sudo apt-get update

And was presented with:

W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/precise/main/source/Sources  Hash Sum mismatch

W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/precise/restricted/source/Sources  Hash Sum mismatch
W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/precise/universe/source/Sources  Hash Sum mismatch
W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/precise/multiverse/source/Sources  Hash Sum mismatch
W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/precise/main/binary-amd64/Packages  Hash Sum mismatch
W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/precise/restricted/binary-amd64/Packages  Hash Sum mismatch
W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/precise/universe/binary-amd64/Packages  Hash Sum mismatch
W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/precise/multiverse/binary-amd64/Packages  Hash Sum mismatch
W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/precise/main/binary-i386/Packages  Hash Sum mismatch
W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/precise/restricted/binary-i386/Packages  Hash Sum mismatch
W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/precise/universe/binary-i386/Packages  Hash Sum mismatch
W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/precise/multiverse/binary-i386/Packages  Hash Sum mismatch
E: Some index files failed to download. They have been ignored, or old ones used instead.

I've seen several variations on how to fix this issue.  Some of the suggestions didn't work but some were a partial of what worked for me:

apt-get clean
rm -rf /var/lib/apt/lists/*
rm -rf /var/lib/apt/lists/partial/*
apt-get clean
apt-get update

Running the last two was suggested but that didn't solve it for me.  Nor did removing the lists as was also suggested in another post.  Running the full set worked for me.  Personally, I'd just start there next time since I don't see any harm in it.