Can you try burning an audio CD now, and scan it?
C2 errors are basically read errors on the CD. Some C2 errors can be corrected by the drive as it reads the disc, but some can't be corrected. If you have very large numbers of C2 errors (like you mentioned in your post above), parts of the disc are probably unreadable. In any case, if you're seeing any C2 errors, there is a problem with the drive, the disc, or the speed at which you burned the disc.
Also, are the C2 errors occurring on both the Fuji and TDK discs you're using, or are they only occurring on one of those brands?