The Silicon Image 3132 eSATA ExpressCard driver is pure evil with Mac OS 10.5 Leopard.
After installing the Silicon Image 3132 driver (to connect to my WiebeTech ToughTech XE mini eSATA enclosure) I couldn't print, copy and paste or connect to file servers. The only fix was to do a complete Archive and Install of Leopard.
I suspected that the SI 3132 driver was the culprit when this happened to me before but I wasn't sure because I installed a bunch of other software around the same time. After some research I realized that many others are having trouble with the Silicon Image eSATA driver with Leopard [Apple discussions, MacRumors forums].
Until SI updates their driver for Leopard, steer clear.
If Apple would only build an eSATA port into MacBook Pros we wouldn't have to worry about this third-party driver incompatibility nonsense.