I think those people are missing a codec - they may be specifically missing
TechSmith's Screen Capture Codec.

Look here for more info on codecs:

http://www.indezine.com/products/powerpoint/ppvideo.html#installed

http://www.techsmith.com/products/studio/codecdownload.asp

hi lee,

yes indeed i am afraid that as geteesh rightly states, it
does sound very much like a codec problem. perhaps you
might consider recapturing the files using one of the non
proprietary codecs like cinepak or microsofts own codecs.

there are plenty alternatives to the capture program you
used freely available out there, as well as demo programs
and trials, for example from companies such as ulead etc.

producing your video files with a non proprietary codec
means that the end user wont have to connect to the
internet to download a third party codec, and you can be
assured your files will play straight away, and in the
manner you wish them too.

hope i've been of some help.

Regards,
Scott Harvey
http://www.123Powerpoint.com