I get an error when ugrading magento from 1.5.1.0 to 1.6.2.0

Question

Hi for the last two days I have been upgrading my magento site gradually from 1.4.0.0 to see if I can get this to the latest stable version 1.8.0.0 and I have come across an error that I can't seem to get past. the error is:

a:4:{i:0;s:56:"Mage registry key "_resource_helper/core" already exists";i:1;s:1414:"

I have been following a process to upgrading I have started from 1.4.0.0 backing up the directory and the database so I do have a working copy, then copied the new files in made sure they work on the frontend and the backend, then i clear the caches within the admin page then create a backup and then do the process again i got up to 5.1.0.0 with out any problems then i try to go to 1.6.2.0 and this error pops up. i have tried clearing the cache and this has not helped.

I just have a few questions that I would like to ask and see if anybody has any answers.

1) Has this happened because I have gone from 1.5.1.0 to 1.6.2.0 straight away instead of going to 1.6.0.0 and then 1.6.2.0.

2) Is there a way to fix this problem or would it be best to restore the site from my backup and then upgrade to 1.6.0.0 or a secondary way

3) Is it something in my database that I can change or something in one of my files that I need to edit.

Answer 1

I fixed my problem within a few steps of it breaking i restored my database and root directory back to the working version of 1.5.1.0 and then I downloaded 1.6.0.0 and then went through the steps I had previously done this then created another error about having problems with renaming a certain file i then went to this directory C:\inetpub\wwwroot\magento\app\code\core\Mage\Reports\sql\reports_setup\ and deleted its contents. then i deleted the cache of the magento and also the browser then my site was working again and i can access the admin panel and everything is working there. I then backed everything up and repeated the process with 1.6.1.0 and this worked as well so now i have currently got a working version of magento 1.6.1.0 thanks for the help and suggestions