Ooh, I think I just came up with something. I'm practicing two bar sections from the end backwards.. so last two bars, then the two before that... This might be helpful. Any other ideas would be appreciated!

When I am home this weekend I will pull out my Neuropsychology textbooks and see what they have to say about it. I know I studied all kinds of stuf about memory but darned if I can remember it all at the moment!

I do know that one very effective technique is association. It can take all kinds of forms, from associating words you need to memorize with pictures, making a story out of them, etc.
As for music without words, though.....I know repetition is effective (both listening and playing over & over & over).

This looks like a good web page with tips about how to memorize music:
www.robertkelleyphd.com/memory.htm

I am a bassoonst, and I used to have a hard time memorizing music. A couple of tricks an old teacher taught me:

* Do what you're doing -- play the last 2 bars, the last 4, the last 6, gradually working your way back.
* Don't start rehearsing at the beginning of the piece, but at section breaks/movement changes and play to the end (of the section or the piece)
* After that, keep your music handy, then start at a random measure and play to the end (of the section/piece) and then loop to the beginning and play to the point where you began
* For getting tricky rhythms under your fingers, vary the rhythm (if it's a passage of 8th notes, play them as dotted-8ths & 16ths and vice versa). Then play it backwards. Then do forward rhythm variations some more.
* Practice in a different place. If you usually rehearse in one particular place in your house, go to a different room, go outside, play in the bathroom (great acoustics!), in the stairwell, anyplace to mix up the setting for your brain.
* Invent a story to go along with the piece, and imagine it in your head as you play. As you're going through the plot you'll be less likely to leave a bit out, because as you associate the piece with events, and you know what sequence of events is necessary for the story, it'll be easier to recall the "soundtrack." (Sounds cheesy, I know, but it worked wonders for me once!)
* And finally, and most importantly, don't beat yourself up over having trouble memorizing. If you get angry with yourself all the time, you're setting yourself up to be afraid of failing, which makes you paranoid, and makes it more difficult to let go and play.

I hope some of that helps! I know it can be a real pain to memorize a long piece.

How's your music theory? Not that you'd have to have the piece analyzed to the nth degree, but I sometimes find it helpful to memorize a piece based on its motives/subjects, countersubjects, and harmonic progressions (at least, their general goals or arrivals...like "The first section begins and ends in CM I, the episode takes it to am...goes through the circle of fifths with such-n-such arpeggiated pattern" etc.)

Although, sometimes, it doesn't work so well for me. My brain got stuck on a motive and wanted to modulate to the wrong key when doing a Vivaldi sopranino recorder concerto. I was hoping a bystander would come up on stage and kick me to get me unstuck.

I have the same problem so, alas, I can be no help. Good luck though.
~*Spoonums*~