Dave,
Make sure that you have DMA turned on- this allows the computer to send data from the hard drive to the CD drive without touching the CPU. This is especially important on older (slower) machines. There are tutorials on the web about turning on DMA.
Defragging is a good idea. R&Ring the recording software may work, becuase it might turn the DMA on for the drive.
With regard to cheap discs and cheap burners:
I burn literally hundreds of discs per year, and I only buy the cheapest possible discs ($10-12 per 100), and I burn them on the cheapest DVD-RW drive I've seen ($50 at Fry's). I only rarely have problems, and these are usually won't play on a specific CD player, i.e. the disc works fine elsewhere.
If you've been having this problem for some time, and you've verified that DMA has been turned on, it might be time for a new burner. My suggestion is to get the cheapest one you can find on line (I'm guessing that newegg.com or outpost.com should have sub-$50 DVD-RW). YMMV, HAND, IANAL.
Brad
PS- I'm not running a bootleg ring; I wrote custom software for our church that records, databases (who, what, when), burns, and prints labels for preaching. Pretty cool.