You must have the 32bit libraries installed to execute the fah6 64 bit client. There are details as to why on the FAH site but just do an "apt-get install ia32-libs" and then run it again. Ubuntu has no multi lib issues like mentioned.
The general consensus on dual core procs is to not run the "-smp" option but if you have a quad core the run it like "./fah6 -smp" and it will work on all cores.
Cheers
Mike