Hi,
The error in that SQL query is this part (if you remove this part, the query runs without errors):
AND ((()))
This SQL query you posted is the result of a PHP code (inside theme’s functions files), code that uses WP_Query with incorrect arguments (most probably empty arguments - resulted from exactly what you’ve said, searching with an empty field).
So, in my opinion, reinstalling WordPress won’t help!
What will help is to contact again the author and tell him exactly what/how you search, so that he can have a look at how the WP_Query is written for that search.
From my experience with this type of error, you just found found a particular situation which isn’t covered by the code. Just contact the author again, explaining step-by-step the reproduction steps and he will know how to help.
