I've been having problems lately. Which burner are you using and at what speeds do you typically burn? I have a Plextor 48/24/48U (USB 2.0) external drive that works fantastic with Retrospect, and EZCD but will not burn any faster than 4-6X speed in CDA5 without buffer underruns. Yesterday I burned a disc with CDA5 "successfully" (with red book compliance) and it would not play in my cd player. I've read many of the responses to similar problems insisting that CDA5 works just fine and that "you shouldn't burn audio at high speeds, anyway" but I don't buy that there's not something going on with the way CDA5 interfaces with USB. I have a five year old Plextor 8/2/20 (SCSI)that worked fine with this same setup until the drive gave up the ghost.
Do you prerender to file before burning? Unless I do that, I have the same problem with a Plextor 16x drive and Windows 98 SE. But I never had to do that with my old 8X SCSI drive.