Of course it must be a Windows 7 issue, and the other 500 million users of Windows 7 just haven't discovered it yet.
Or perhaps, if you provided a little more information.
What kind of disc's. Brand and type. By your title I would assume you are using the same disc for both audio and data, and depending on the disc type may not be possible.
What burning software (a few different ones is not helpful) and versions?
What is the error message from the burning software?