As mentioned by rdgrimes, the easiest solution would be to steer your client away from InCD.
Otherwise, the client should try several brands of CD-RW media to find out which media are suited to his burner. You didn't tell us what burner and media types he had been using, but for faster burners it may be difficult to find reasonable Ultra Speed (16x-24x) media; e.g., Memorex should be avoided, but Verbatim is usually OK (except for some batches).
Further, your client might be too impatient, trying to eject a disc immediately after some operations. It may be wiser to wait until cached writes are finished.