Error Log classes.php Missing

Hi everyone! Thanks for reading this.

– I have been trying to upgrade one of our sites from 2.x to 3.4, and finally gained Administrator access yesterday. (Our IT guy moved interstate in 2011 with the admin password).

– During the upgrade to 3.4 we ran into difficulty. Because of the age of the old wordpress and plugins (2.4.8 I think), there was no ability to create a backup, despite many attempts.

– I followed http://codex.wordpress.org/Upgrading_WordPress_Extended as best I could.

– We have the added trouble of using Parallels Plesk 9.x as our FTP thing.

– I have been getting assistance from our web host, but I think I’ve used up all their good will. They sent the following email earlier today:

In order to resolve your issue, I have gone through the error log and
found below relevant information.
—-
tail -f error_log
[Mon Jun 18 14:57:53 2012] [error] [client 192.84.19.22] PHP Warning:
require() [function.require]: Unable to
access /var/www/vhosts/brutalart.com.au/httpdocs/wp-includes/classes.php
in /var/www/vhosts/brutalart.com.au/httpdocs/wp-settings.php on line
248, referer: http://brutalart.com.au/property-development/subdivide-land/
—-

It appears that there is classes.php file missing. Have you taken backup
before upgrading wordpress? If yes, then upload it in httpdocs/test
folder through ftp.

Once we have restored the backup, we can upgrade it from wordpress admin
panel.

Awaiting for your reply.

As mentioned, we do not have a back up, so we have no ability to upload it.

Is there another way of resolving our troublesome wordpress issue?

All the best,
Breece