I've tried to deactivate/activate the plugin after playing with the settings and the site went offline with an error message.
I'm suspecting that one of the files might have been extracted incorrectly and missing characters or perhaps lines. I have never seen this kind of behavior before, missing/incorrectly uploaded files might explain it.
I'm sorry about the error, I wasn't expecting that, you will have to rename/delete the wp-content/plugins/ajax-search-pro directory to get rid of it as it looks like a syntax error.
If you could also provide temporary ftp access it would be better, as I was able to make direct modifications to the search code in case of something like this happens.
Also, try to re-install the plugin once after deleting, it might help. If not, then I'll debug through the code to find the cause.Best,
If you like my products, don't forget to rate them on codecanyon :)