The following is copied from Apple's website (http://docs.info.apple.com/article.html?artnum=307231):
"Mac Pro (Early 2008): Dongle may not be recognized
Last Modified on: January 08, 2008
Article: 307231
Some applications use an external hardware device that connects to the USB port to authorize the use of the software on your Macintosh. This device is commonly referred to as a "dongle."
If your application is having trouble locating a dongle that is plugged into a display or keyboard, try plugging it into one of the USB ports on the CPU. This should allow your application to more easily locate the dongle and authorize use of your software.
Note: If issues persist on the Mac Pro's USB ports, refer to the third-party vendor that provided the dongle."
(Can't wait for this!!)
Also the following (http://docs.info.apple.com/article.html?artnum=307149):
"Mac Pro: Noise, pops or clicks heard when monitoring a live recording
Last Modified on: January 07, 2008
Article: 307149
If using an audio recording application on a Mac Pro (8-core) or Mac Pro (quad-core), noise, pops or clicks may be heard while monitoring the recording.
These artifacts are only present while monitoring the recording and are not present when the recording is played back."