From the changelog:
"Add a new method for drawing fog of war (gtk2-client and win32-client only). Change the trident tileset to use this new method."
Hmnm - I tried the win32 client. With the trident client, fog of war seems to be not drawn at all. I guess iso_trident was meant, where FOW is drawn. All other tilesets seem to be unusable right now sadly.
UPDATE: with the gtk2 client the trident tileset shows indeed a new and nice looking FOW. So it seems its only the win32 client that behaves different than the changelog suggests ...
Suggestion: send a bugreport to bugs@freeciv.org
While waiting for a new beta though, you can get around this bug by toggling the new fog option in local options off and on again.
This report isn't very clear. Are you saying the win32 client doesn't work on windows, or the gtk2 client doesn't work on windows? The wind32 client shouldn't even have the "new fog option" available. --Jason