Internet explorer and Firefox are unable to play back a video on Screencast.com, clicking play brings up a Please wait.... the video is loading popup.
The most likely cause:
Any video larger than 1080 pixels in height will run into this behavior. On windows, Firefox and Internet Explorer rendering engines are unable to process HTML5 video playback larger than 1080 pixels in height.
Remaking the video at a size smaller than 1080 pixels high.
Use a tool to make the dimensions of the video smaller (like Camtasia for Mac, Camtasia Studio, or other editing software).
Upload the smaller video to Screencast.com and check the results in the effected browsers.