How did you go with this? I've not seen the problem crop up on my 360 (original) for months now. I've mostly been reading (gasp) paper books, but have gone through about 1500 page turns across two ebooks in that time, and books I was reading previously would incur this stripey problem every 100 pages or less.
I was starting to wonder if it may be triggered by ebook content - though this goes against my understanding of the problem - but on the off-chance, I loaded up one of my old Flashman ebooks that used to exhibit the problem, and just hit page-next while watching some TV one night. No joy at all (well, joy insofar as no stripey-screen). Very frustrating, especially as I'm coming up to the anniversary of the machine, and I just know it's going to manifest again as soon as that day comes and goes.