Dark pixel glitch with multiple response

I'm having a strange problem with my multiple response questionnaire. I'm attaching test.exp which has a testintro1.que and a choice1.que. Testintro1.que only has an instruction item. Choice1.que has 3 multiple response items.

When I run test.exp, several dark pixels appear under the first button for all of the items in choice1.que. It happens with the instruction text (in testintro1.que) in particular, even when I change the spacing or delete a word. When I changed the instruction text to:

a
b
c
d
e
f

the dark pixels went away. Does anyone have any idea why the content of the instructions would matter? It doesn't happen with scale response, but this questionnaire is multiple response because we want to prevent the participants from clicking through the questions rapidly. Alternatively, is there a way for the cursor to appear in a different location after a button is clicked so that the participant can't just click again? The only option we thought of is to change the location of the responses from question to question, but is there any other option?

Thank you very much!!

In order to prevent users from quickly skipping through questions, you may want to see if the 'o'nset parameter can help.
[url]http://www.empirisoft.com/medialab/help/queparameters.htm#onset[/url]

It would seem that the glitch you've found depends on what the 's'pacing parameter is set to. I've never seen this bug appear; however it seems that changing the 's' value can remedy the problem. Let me know if you need more help with this issue.

Hi, thanks for your reply. Changing the s parameter didn't fix it -- it's really a very strange error and I'm not sure what it was. However, I fixed the problem by including a blank item with a 1-second duration, and that seemed to "clear" the screen so that the dots didn't appear.

Hm - great to hear that you were able to find a solution to the problem.
Thank you for posting what you discovered about the bug.