Some notes on testing with your prototypes:

1) Pay attention to what users do, not what they say.

2) Don't lead your users. Give them a task, and then watch what they do.

3) It's an observation, not a conversation. Don't totally shut down, but don't banter away either. Be a scientist! 

Here are a couple of excellent articles from Nielsen about usability testing:

http://www.nngroup.com/articles/first-rule-of-usability-dont-listen-to-users/

http://www.nngroup.com/articles/talking-to-users/