Lesson

I am a newbie, so bear with me please.

I just installed Moodle4Mac, and am having some problems.
After adding a lesson, I am adding a new multiple choice question to it.
However, when I take the question as a Student (by assuming the Student role), after it shows me the response (right or wrong), it shows an error page which says:
"ERROR: Mixed types of sql query parameters!!"

What could be causing this?
Thanks!