When some of my users try to view my DHTML Lesson within a web browser, this error message appears immediately, as the lesson is trying to open:
The following error has occurred:
Unable to get property 'stop' of undefined or null reference
The error message is directly tied to the installation of the Windows Media Player on that user's computer.
If this is a new computer and they've never opened the Windows Media Player application yet (or if a major update has been applied to the Windows Media Player), then the Windows Media Player is un-configured.
Open the Windows Media Player application (from the Windows Start Menu) to allow it to automatically walk you through a quick configuration wizard. Once configured, the Windows Media Player is fully functional and this problem should go away.
When launching a DHTML lesson, two Windows Media Player ActiveX controls are automatically initialized to play a very short and silent sound clip. Under some circumstances initialization of these players can cause unwanted side effects or even errors on certain systems or in certain browsers. If your lesson does not use media-clip type question feedback, you can workaround these unwanted side effects or errors by turning OFF the automatic initialization of these players.
Learn more here.
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