Failure to power off a Tempo card before ejecting it may have an unpredictable result for OS X.
You should follow these steps:
1. Unmount any drives attached to the Tempo card by dragging them to the Eject icon in the dock.
2. Click the Card's icon in the menu bar and select "Power Off Card" from the drop down menu.
3. Push and release the Tempo card to eject.
Sonnet has isolated the occurance of drives not mounting in 10.7.4, which occurs only in 32-bit mode with the Tempo SATA E4P, E4i, and Tempo SATA Pro ExpressCard/34. Users running in 64-bit mode will not experience any issue. (To boot in 64-bit, hold down the 6 and 4 keys when the Mac starts up.) Install driver 2.2.9 or greater to fix the 32-bit mode issue.