The answers questions not selectable in quiz slide for some users
We have a SCORM Captivate training content published on our LMS (SAP Learning Solutions). Some users can't respond to any questions in the content.For these users, the answers are locked and are not selectable. Also, the Validate and Erase buttons didn't appear.
The problem concerns about 10% of our users.
This training contains both content slides and quiz slides.

The content is published in SCORM 1.2 (SWF + HTML) with Adobe Captivate 5.5. We had the same problem for some users with the previous version of this training content published with Captivate 4.
All users have the same settings:
Flash Player 10.3.183.11
Internet Explorer 6
Microsoft Windows XP