For some reason, one of the indices used by the upgrade manager(s) is not downloading properly, that is the download of http://archive.ubuntu.com_ubuntu_dists_ ... 6_Packages
when checked against the hash used to check that it gets a good download is reporting the error. The only thing which I might suggest is to repeat updating your packages until this error is fixed. The sudo apt-get update
terminal command is one way to check if the update download finishes without error.