[Lynne]

That's just fine. The error is here:
MySQL Error : Unknown column 'language.phrasegroup_prefix' in 'field list'

However, there is no column 'phrasegroup_prefix'' in default vbulletin, so as suggested above, you have a plugin installed that is causing this error.

I would try turning the plugins off through the config file by adding this someplace after the first line:

PHP Code:

define('DISABLE_HOOKS', true); 


See if that fixes the problem.