I remember trying to get Xsyon to run under wine on OS X. I managed to get the game to launch and log in, but if i remember correctly, the shadows were messed up in a similar way you are describing now.

On that note I don't remember getting an error message in the launcher. But that was a different version of the launcher.

On that note, trying to get it to run under wine also reveals all the required libraries and runtime the game needs to run. Which for whatever reason are not included in a clean install of Windows anyways. Cause I could not launch it in Win7 when I put a fresh install on.