doubt this will go anywhere but on the demo version this occurs.
img/system/WindowThink.png failed to load pops up when trying to progress through the start of a new game just after you encounter the surprise orc boss when entering the dungeon for the first time. Also when finishing the boss fight with high lust with or without the 3rd party member on the old beta 0.5 version save i had.
Sure I'm doing this on the android phone browser but it has worked fine before. Thought it was the old save being the issue but seems that even the new save has issues.
Again, highly doubt this goes anywhere but it does seem like a bummer for any new players wanting to try out the demo to get a taste of the full game.