There is no 64-bit overlay support so this is odd. Does is crash on start or when it's running?
Take a look at: https://gist.github.com/4421577. This game did require a replacement of RenderSystem_GL.so to access «Settings» in the game without crashing, but I have successfully completed the demo with the overlay disabled.
The game crashes on start. I do not have an access to a ubuntu box right now, both the messages is the same as other ppl get something like this when overlay is enabled:
ParticleUniverse: Particle Emitter Type 'Entity' registered
*** Initializing OIS ***
X Error of failed request: BadAccess (attempt to access private resource denied)
Major opcode of failed request: 2 (X_ChangeWindowAttributes)
Serial number of failed request: 7
Current serial number in output stream: 8
AL lib: ReleaseALC: 1 device not closed
Game removed: AppID 226540 "The Book of Unwritten Tales: The Critter Chronicles Demo", ProcID 2311
See here, for ex. - http://steamcommunity.com/app/221410/discussions/1/846938351170700382/
We'll have a fix for this in the next client update.
Game crashes on Ubuntu 12.10 x86_64 if Steam Community overlay is enabled. Apparently, this affects other users as well (see hub for Non-Valve games)