Installing and upgrading help

I am attempting to upgrade from moodle 1.6.1 to Moodle 1.8 using CVS.

My old version of moodle was located at http://willcarey.nsw.edu.au/ and I installed it originally by downloading the moodle zip, extracting it on my home computer and then uploading the files via ftp to the web root folder on the server, then following the install procedure

I attempted to use cvs to put the new version of 1.8 at http://willcarey.nsw.edu.au/moodle/ and copied the edited config.php with the old database details and new path details and am now stuck in an installation loop.

The installation stops after upgrading the database with the major error "there is already a role with this name!" and when I press continue I am returned to the original http://willcarey.nsw.edu.au/moodle/admin/

(Since the original install I now also get a whole lot of "this table already exists" type errors <-- where the db has already been updated to v1.8)

I thought I had successfully backed up the 1.6 database by doing an sql dump however have now discovered after attempting to restore the old db that the backup is corrupted. I do have a copy of the original user data folders, but this doesn't seem to help me.

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If all else fails I do have nightly backups of the courses we have created and I could always do a fresh install of 1.8 and then import the courses again but thought I would try to find help here first in case this is an issue for other upgrading from 1.6 ->1.8

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The old version of moodle 1.6.1 is still successfully working at http://wilcarey.nsw.edu.au despite the db upgrades.

Any suggestions and or help would be appreciated.