UAC is the Windows User Account Control, used in both Vista and Win 7.
By default it is set to "on". If it is "on" then it prevents software from writing to your disks without your knowledge. So when EAW tries to write to its own "eaw.ini" file UAC will not let it and EAW crashes. This problem does not occur with UAC set to "off".
Do a search for it in "Windows Help".