[bobfffg]

if you're laser is struggling, yes placing it in a vertical position can help sometimes... that was the case with the original playstation too.

do you older cd-r backups still work or is it just the last three you've written? might be worth running a diagnostic on your burner too.

if you're laser is going, try burning with a different type of media. sometimes that can overcome the problem, but only temporarily until the laser starts getting worse.

if you can afford it try an flog your old v4 and get a newer model.