Simply change the registry key HKEY_CURRENT_USER\Software\Blizzard Entertainment\StarCraft II Editor Beta\Preferences\Locale
from enGB to enUS
It seems that the beta installer may set the wrong locale to the beta editor, if you downloaded the enUS client and the registry says enGB, the editor won't be able to find the correct locale and will crash
I found the solution with dele ;)
Simply change the registry key
HKEY_CURRENT_USER\Software\Blizzard Entertainment\StarCraft II Editor Beta\Preferences\Locale
from enGB to enUS
It seems that the beta installer may set the wrong locale to the beta editor, if you downloaded the enUS client and the registry says enGB, the editor won't be able to find the correct locale and will crash