I have a quick question for you. Are your burns from files on the Hard Drive or are you trying to Copy a CD directly to the burner? You stated you have your burner and CDROM on separate IDE channels. That is good but one thing I have found. Some CD's (especially burns and CDR/W's and some poorly made pressed CD's) will not read as fast as a well made CD. If the reading is slow enough and you don't have a burner with Burn Proof and are going directly from the CDROM to the Burner with no image file to the HDD first, you will get buffer underruns as the Reader can not keep up with the burner. What I do if I suspect a CD is try a quick file copy to the HDD and see if it copies as fast as it should. Since I have been doing that I have not had one coaster in a LONG time now. I never get a coaster burning from the HDD. Now that I check my CD's first I do not ever have a problem coping a CD on the Fly to the burner.
Also those that suggested you try Nero are correct. Ever since Roxio took over Easy CD is not the program it once was and from all I have seen Nero was always better anyway. Make sure if you are running Windows XP and you get Nero to get the latest version. Older versions will not work under XP.
One more thing, if the CD is reading slowly in the reader just have Nero use an Image file to the HDD first. Will save you a coaster every time.