Error 1146 after importing answers from Wordpress

Question

 

I found this very great software, Question2Answer, and I have integrated it with my Wordpress website: all worked fine.

So I have imported, from my Wordpress site, about 1500 questions and 2500 answers into my Question2Answer, perfomed database maintenance, and everything seems to work fine except the following problem (I have a dedicated server and other my sites on the same server works fine)

I have the following error "Question2Answer failed query: SELECT qa_users.userid, handle, level FROM WHERE qa_users level> = 20 ORDER BY level DESC Error 1146: Table '. Qa_users' does not exist" if:

1. I do a search on the site (so I have replaced it with Google CSE)
2.  I add a question
3. if recaptcha is active

Thanks in advance

The website is: http://www.aipsimed.org/risposte/