This refers at least to Mac OS 10.6.4 Snow Leopard (or higher) and 64-bit enabled systems like a Mac Pro ... 10.5.x in 64-bit might also be affected.
To enable "Garmin ANT Agent" to connect to devices like Forerunner 310XT - via the ANT USB a certain kernel extension is installed:
/System/Library/Extensions/SiLabsUSBDriver.kext
The version installed with Garmin ANT Agent 2.1.6 (19th of May 2010) is more than a year older (dated 5th of May 2009) and obviously only works in 32-bit mode. If a Mac runs in 64-bit mode - as more and more systems might do - ANT Agent constantly asks to connect the stick, though it definitely is connected physically. Connecting to a device won't work at all. No reason is given.
After a lot of reading FAQs, googling, unloading and loading the kext, guessing and fighting off despair I finally found out that this behaviour is related to the 64-bit mode. Start your Mac in 32-bit mode and connection works flawlessly. To achieve this hold down both the keys 3 and 2 at startup (hold down 6 and 4 to start in 64-bit).
At the time being the difference probably will not recognizeably show with other software and most users won't even know (or care) if their Mac runs in 64- oder 32-bit. At least so did I - but that might change.
To avoid frustration: Could the "kext" maybe be updated by the Garmin software engineers to function with a 64-bit Mac and its current OS?
That would be great.
