Changing the Select Search Implementation from DB Search to Sphinx Search

[fodbrothers]

Select Search Implementation
from
DB Search
to
Sphinx Search

so when I select Sphinx Search and click go the website goes down but still able to access the admin cp
so I go to
maintenance / general update tools
and Rebuild Search Index
hoping this would sort the website out.
but the website is still down and has the following
A System Error has occured.
The software is experiencing a systems error.

You should attempt to repeat your last action. If this error occurs again, please contact the site administrator.

many help would be grateful