I cannot get a working installation of the Unity Web Player. I have read the responses to other installation issues on this forum and I have seemingly exhausted attempts at un/reinstallation by carefully closing browser, rebooting, etc. It seems that many users are having this issue. I was becoming excited at the aspect of development with Unity but it’s hard to be enthusiastic when I can’t get the plugin to work.
When I go to the tropical demo, the loading bar creeps across and then there is an error. An option for manual install and the error message " failed to load Unity dll "
When faced with these problems it helps a lot to know what browser and OS you have. The general approach is to uninstall the existing plugin. Use Control Panel Add/Remove Programs on a PC, or locate the plugin in /Library/Internet Plug-Ins and drag to the trash on a Mac. (Oh, and then empty the trash). Reboot the machine. Now check that the plugin really has gone. On a PC you’ll need to look in your AppData\LocalLow\Unity\WebPlayer folder (or in Program Files if you installed for all users.) On a Mac just check that the plugin is not in the Internet Plug-Ins folder. Next empty your browser cache. This is essential, since it’s possible that the browser has downloaded an old or broken copy of the installer. Then download a fresh installer to your desktop or download folder. Quit the browser and then run the installer. This only installs one of three components. The others are downloaded when you view content with Unity WebPlayer. Then go to our gallery, and perhaps choose the Angry Bots demo. If you are familiar with FireBug, Fiddler or IE Developer Tools, it’s worth watching the page and checking that a couple of zip files are downloaded. These will have the Mono and Player components that are needed. The webplayer plugin should fetch these and install them behind the scenes. Only once these components are installed will you see the Unity content. On a PC these components are installed into the mono\3.x.x and player\3.x.x folders. On a Mac they live inside the Contents/Frameworks folder for the plugin. (Actually, on a Mac these are installed by the installer and not fetched…)
Things that can go wrong are the fetching of the Mono and Player components returning corrupted files (or incomplete files) or Anti-Virus software preventing these components from being installed.
I have marked this as a community wiki answer, so please feel free to chip in comments and fixes.
I have had a similar problem caused by McAfee antivirus on Internet Explorer 8 on Windows 7 (Firefox and Chrome had no problems). It’s currently being investigated by Unity.