Problem upgrading from 6.06.2 LTS to 8.04.1 LTS

[Rich Carreiro]

I'm trying to upgrade from 6.06.2LTS to 8.04.1LTS.  It's
a remote system, so I don't want to use update-manager.
I have dapper-updates activated and have installed
update-manager-core and have everything up to date.

When I run:
   sudo do-release-upgrade -d
I get the errors about hash sum mismatches.  Googling
on that I see I can just leave off the "-d".

But when I do that, I get the "Unable to calculate upgrade
message".  I don't believe I have anything weird installed
(how can I tell?).  What is the process for debugging this
to see what is preventing do-release-upgrade from
performing the upgrade?

Thanks!

--
Rich Carreiro                            rlcarr at rlcarr.com