Told to install Web Player when testing in browser. Web Player already installed.

I have a problem that has become very infuriating.

Previously Unity Web Player worked fine on this computer. However, shortly after installing the Unity development software, it stopped working.

While trying to play any Unity game in a browser, it will just pop up with a message saying that it's not installed, and linkd me to the download page. It says it's still installed when I go to the browser's add-on screen.

This happens in both IE and FireFox. I've tried uninstalling and reinstalling both the player and the dev kit multiple times, without any change. One odd thing I noticed was that after uninstalling the web player AND the dev software, the web player still showed up in the Firefox Addon menu.

I had a laptop which I could run the web player on, but again, shortly after installing the Unity dev kit on it, the web player stopped working. This means I can't test my own games in a browser, rendering Unity virtually useless to me.

Any help would be much appreciated because I'm going to have to drop Unity if I can't fix this.