Sorry for hjacking the thread, but I already submitted this issue a long time ago (alpha versions, ticket ID: QKG-895-56277) and the problem still persists in the latest beta.
It's related to having a non-english symbol/character in the user's profile path.
Log Fragment (debug.err)
Debug Message: Attempting to allocate memory of size: 53477376 bytes
Debug Message: Allocation successful
Debug Message: Game Saved.
DebugMessage: Error writing save data to file Q:\Users\%USERNAME%\Documents\My Games\GalCiv3\Saves\\~test.GC3Sav.
DebugMessage: Deleting save game. Curr. Memory Usage: -1824493568 bytes
%USERNAME% Contains accentuated characters in my case
This happens both for saves and the ship designer.
Is there any chance to get this solved soon?