Game code (ui_mp_x86.dll) failed pure server” error occurs when you try to join an ET server. The reason of “Game code (ui_mp_x86.dll) failed pure server” error is, that one or more of your pk3 files in your ET folder are corrupt, in other words are modified.
a, Set Enemy Territory to ‘Run as administrator’.
In your ET installation folder right click on ET.exe -> Properties -> Compatibility tab -> check “Run this program as an administator” and run the game.
b, It might be a setting causing the “Game code (ui_mp_x86.dll) failed pure server” error, on Vista or Win7 systems: try disabling User Account Control (UAC).
For this, do the following:
Open Control Panel and type “UAC” in the search box -> click on “Turn User Account Control (UAC) on or off” -> Uncheck the checkbox for “Use User Account Control (UAC)” -> click OK -> Restart your computer.
c, Another solution is to completely reinstall Enemy Territory. (Don’t forget to backup your etkey before deleting it!)