This article discusses why Virtural Memory should be turned off when using Final Cut Pro.

Using Final Cut Pro with Virtual Memory turned on is not advised. Virtual Memory can potentially cause dropped frames on capture and playback, as well as sluggish performance.

To turn off Virtual Memory, quit Final Cut Pro, open the Memory control panel, and click the Off radio button (see Figure 1).

Figure 1 Memory control panel with Virtual Memory turned off

Once this is done, close the control panel and restart the computer for this change to take effect.