I do not have any problem using VLC or the download button with IQS.
But you could try just using the IceDivx to access the player.
On the front page right hand side under friends their is a ice cube and the words IceDivx
or this link you could bookmark it http://www.icedivx.com/
Now when you open the IceFilms link to the source you want to watch then copy the URL,and go to that page and and enter it and it will generate the embedded player I.E. the IQS player. Which some people use if they don't want the hassle of installing the IQS script.
Other than that it would be prolly just the Divx Player.
Unsupported file format/codecs/something that just don't jive with Divx
You could try using VLC or any other player that will open a .m3u file type
VLC/Zoom Player/SM Player/ and I think Windows Media Player Classic(WMPC) tho I'm not 100% on WMPC
<But there are lots of players that will just search for it and pick one>
You will have to of course change you default open with for that file type on Windows. I don't know anything about MAC so you will have to figure that out on your own. If you don't know how again search for how to.
Hope this helps or gives you another option.