Just in case you missed it: Silicon Labs (SiLabs) now offers a 64-bit driver version for its CP210x USB to UART bridge virtual COM port. These chips are found in quite a few GPS loggers, e.g. the Holux M-241. The latest version also contains a few fixes:
Corrected Kernel Panic in Snow Leopard which would randomly occur after
Modified DTR pin to toggle on open and close instead of on insertion
Modified driver to load without showing the Network Connection Dialog
Modified driver to allow toggling of RTS and DTR pins
Added 64 bit support for Snow Leopard
So if you’re running Snow Leopard in 64-bit kernel mode, head over to SiLabs website and download the new driver.