I am having the same trouble, although with different files.

My 7.10 online upgrade was flawless. Had to be, I am a Linux junkee, just
experimenting and learning.

The 7.04 installation was from the CD enclosed with the book Ubuntu Unleashd
2nd ed., and had all upgrades offered online. . PIII, 384MB ram, dual boot
with XP

Do not use Automatix to upgrade!..............

You can also use the "restore repositories" option in Automatix and
then upgrade (this should also work)

A new automatix for Gutsy is available at this time

if the error persists, open a termina and type

sudo gedit /etc/apt/sources.list

find the entry with lowvoice.nl and place an # before it.

save the file and start the upgrade again.

This will fix the problem.

well at least you are not getting a kernel panic error.
It it is really sucking my day
http://ubuntuforums.org/showthread.php?t=584416

I had the exact same problem. I also uninstalled Wine and had the same
error again. This is how I fixed it. Go to System > Administration >
Software Sources (you'll have to enter your password) > Third Party
Software. Select the "http://wine.lowvoice.nl" entry then select
Remove (at the bottom of the dialog box), close the box and try the
upgrade again. This worked for me.

During the "Preparation to upgrade" all is going well then I get;

Failed to fetch archive.ubuntu.com/ubuntu/dists/feisty/Release
Unable to find expected entry main'./binary-i386/Packages in
Meta-index file (malformed Release file?)

New to Linux and have no idea as to where to go, my system running
7.04 is up to date and internet connection is good.

Any help?

I had this problem and this fixed it:
http://www.ubuntu.com/getubuntu/releasenotes/710
Read the commercial/partner repository part.