Using MyDVD 4.5 that came with my burner. (I know there are better authoring programs, but this was free & it works - usually). Burnt a bunch of chapters to a DVD+RW disc. Added some more using Update Current Disc, no problem, only the new chapters were transcoded. Now I want to add some more, but when I open the disc for editing and hit Burn, the Update Current Disc option is greyed out, the only option is Create New Disc. This will re-encode all the clips and take way longer. Any idea why the Update option should vanish? I wasn't using the Create A Hard Disc backup First option, but that didn't cause problems previously.