Arduino problem with Snow Leopard?


I am trying to use arduino board with Director 11.5. It is running from MacMini, FTDI Serial, Snow Leopard using PhysicalBits Serial Xtra. For some reason, it only allows a certain number of commands (about 60 lines) to be sent before the connection is dropped. After that, the computer & connection freezes and the only way to get out of it is to reboot. Is there any known incompatibility in the system that I am using?

JTD :'(