As Tobias pointed out, depending on the Mac OS you're running you should make sure you have the latest version of Quicktime.
You may also be experiencing buffer underrun which can be caused by a lagging or fragmented hard drive. Do your music files reside on the start up drive? This is usually a bad thing as this partition is by far the most prone to fragmentation, master blocks being corrupted and so forth because of the hundreds of thousands of tiny files a system or system file contain.
The best thing to do is to have all your music files on a separate storage device or different partition that has been recently optimized.
Also, in the past myself and other co-workers in the design field have found Memorex media to have higher failure rates during burns. This was 6-8 years ago and may not be an issue now. But that is why I prefer to use Mitsui or Sony for CDs and TAiyo Yuden for burning DVDs.
Burning CDs and DVDs hogs processing power, so working in other applications while burning can be a risky thing. I've been using Toast since I think 1996 and notice these days that is never a problem when burning CDs. I can even manipulate 2 gig Photoshop files while burning CDs without problems.
However, DVDs are a whole 'nother issue. I can't even surf the net while burning DVDs. It's hit or miss if they'll pass verification if I've been active in other programs during burning.
You seem to have a fairly new computer so I would recommend working in OS 10.3 Panther using Roxio Toast 6 to burn your CDs. I've never used iTunes for this as I've found over the years Toast to be a very stable and reliable solution. Toast also has a simulation mode that allows it to go through the whole process without actually burning a CD. IF it fails during this, then you've saved a CD and may have a corrupt music file, a fragmented drive or a drive in need of a disk Utility.
These days because of the better software and CD/DVD burners, I find I never have to run simulation or verification for CDs, but I do verify DVDs as they are more prone to failure. CD and DVD media is also more reliable now.
Another thing to try is to burn at a slower speed. I know it's tempting to burn at fast rates, but slower speeds are more reliable and many say sound better too.