Apple posted an EFI Firmware update for Mac Pro owners today. The update "fixes several issues to improve the stability of Mac Pro (Early 2008) computers."
Once you download the update, you must run the Firmware Updater and follow the enclosed instructions for the update to take effect.
To update the firmware on your Intel-based Mac Pro:
1. Quit all other open applications.
2. Click Shut Down in the Mac Pro EFI Firmware Update window and wait for your computer to shut down.
3. Press and hold the power button on your Mac Pro until the status light flashes repeatedly or you hear a long tone, then release the power button.
A status bar indicates the progress of the update. Important: Do not interrupt the update. Your computer restarts automatically when the update is completed and opens the Mac Pro EFI Firmware Update.
4. Click OK, if the firmware is now up-to-date.
