Just a note of interest.
You don't mention the brand of CD and DVD's you use.
Remember there is a huge difference in the Media you buy and choose.
There is also a big difference in the Software you use to burn with.
There are several schools of thought on th entire subject of burning period.
Apple burners are historiclly very picky, and do not like CHEAP Media.
Here is a good guide to use, it is for DVD but I would use like brands with CD's
http://www.digitalfaq.com/media/dvdmedia.htm
As I mentioned above the software you use can and does have an affect on your success.
http://docs.info.apple.com/article.html?artnum=303599
As well as the burning assist link above using Apple Software, don't forget, Roxio's Toast 8 is considered the easiest and best for Mac users
http://www.roxio.com/enu/default.html?ccid=google&o_e25=Paid%20Search&gclid=CJuG 9uLNiogCFQ9OWAod014AHg
My quess is your problem is Media
Don