Unity client working in Opera but not in IE

I've installed the unity client (downloaded via Opera), and it seems to work there, but when I switch to IE and visit the same page, it says I need to download the unity client. Is there s specific client for IE as opposed to Firefox/Opera/Mozilla?

If not, does anyone know what to do about it?

The client is the same, that isn't the problem.

It may be an IE configuration issue. There are two things (at least in Opera) that I need to enable for Unity to run - Javascript and Plug-ins. If you hit F12 in Opera you'll see them, presumably enabled by default. It's possible that IE has one or both of them turned off by default. Or it might be a case-by-case basis to enable Plugins.

Try Tools->Manage Addons to see if the Unity plugin is enabled in IE.

To see if Javascript is enabled in IE7.