i just installed rxtx.x86_64 (for fedora 10 currently: 0:2.1-0.2.7r2.fc10)...
and removed the lib/librxtxSerial.so file in the arduino 0013 directory
and soft-linked /usr/lib64/rxtx/librxtxSerial.so to lib/librxtxSerial.so...
it can compile and upload on amd64 now... natively... 
WOOOT!