We have seen on some occasions where Internet Explorer is unable to play some clips but they work fine in other browsers.
Try this setting change to Internet Explorer to remedy this occurring.
Open Internet explorer and choose the settings (cog/wheel) in the top right
Choose 'internet options'
In the window that opens choose the 'Advanced' tab
In 'Accelerated Graphics', tick the 'Use accelerated software instead of GPU rendering'
Select Apply and then OK
Now close all IE browsers you have open
Reopen IE and play the link.
Here is a quick link to show you how.