[BirdOPrey5]

Hmmm... the only scheduled task that runs on the 20 after of every hour by default is called Hourly Cleanup #2. which is the file ./includes/cron/cleanup2.php.

Whatever is causing your error is in that file... The fact this is a default vbulletin scheduled task strongly suggests the problem is related to your failed upgrade.

Further investigation I confirm the table "repimage" was removed from vBulletin starting in 3.7.0 so you have code from 3.6 and code from 3.8 conflicting.
Some details here. (In the quote.)

Basically you're going to probably need to do a complete/full upgrade to fix this.

If you wanted to simply get rid of the error without fixing the problem go to your phpmyadmin and try creating a new table called PREFIX_repimage where PREFIX is your table prefix you set on config.php. This *may* work but isn't a good long term solution.