If you are upgrading an old version of Vbulletin to the latest release and you already had the skimlinks plugin installed you'll probably run into issues.
Basically the vbulletin upgrade can't handle the upgrade of the plugin properly, so you get loads of SQL errors (and if you get an email for each one on busy site your inbox will soon be flooded)
The solution is as follows:
Uninstall the Skimlinks plugin
Then re-install it by importing it from the file system:
./includes/xml/product-skimlinks.xml
You'll need to use the vbulletin installer / upgrade system to complete the install and then the SQL errors will vanish
Nice explanation of it here: vBulletin 4.1.2 Upgrade error: SkimLinks Table
Basically the vbulletin upgrade can't handle the upgrade of the plugin properly, so you get loads of SQL errors (and if you get an email for each one on busy site your inbox will soon be flooded)
The solution is as follows:
Uninstall the Skimlinks plugin
Then re-install it by importing it from the file system:
./includes/xml/product-skimlinks.xml
You'll need to use the vbulletin installer / upgrade system to complete the install and then the SQL errors will vanish
Nice explanation of it here: vBulletin 4.1.2 Upgrade error: SkimLinks Table