In Final Cut Pro 5.1, the QuickTime variant of the Sharpen filter may produce undesired coloring artifacts when used with images or video clips that contain an alpha channel. This only happens on Intel-based Macs.
The effect where this is noticed is:
Effects > Video Filters > QuickTime > Sharpen
To workaround this issue, use an alternative filter, such as:
Effects > Video Filters > Sharpen > Sharpen
This document will be updated when more information becomes available.