Crossover doesn't support every Windows only program and I expect something new such as AC2008 won't be supported straight away. In my experience Crossover doesn't really work that well at all anyway.
If you really MUST run Autocad (there are lots of dwg compatible, and some would say better, CAD systems available for OS X) then you will seriously have to consider running Windows through Bootcamp, or a virtual solution such as VMWare Fusion or Parallels to get anywhere near a reasonable usage level from something like Autocad.