if there was a way to change the booktype setting to write the dvds as dvd rom, i would recommend that. i did that on my desktop's lite-on burner, and it changes the dvd +r booktype to make regular dvd players think the dvd +r is a dvd rom so it is more compatible.
i don't think you can make this change on this drive, at least i haven't found anyone with the information, yet.
i have the gca 4040n in my laptop, and it is much quicker than the desktop (laptop cpu is 2.66 ghz, desktop cpu is 800 mhz)
i use dvd shrink and dvd decrypter for all my backups with the gca 4040n and i have had no problems at all with dvd +r, the gca 4040n is much less picky with blank dvd +r media than the lite-on burner is. pretty much every type of blank dvd +r i have tried has worked in the 4040n.
for your problems, i would suggest getting good dvd +r media, preferrably something made in japan or singapore, find dvd identifier on the web and download it and check your media, if it is cmc-xxx-xxx it is most likely crap. do a yahoo search for how to find good dvd media, or search in this and other dvd forums
you can't use dvd -r in the 4040n, so spend the money for decent media like ritek or verbatim dvd +r
i would also suggest trying to use dvd shrink and decrypter together and see if that solves your problem of dvd +r working to backup.