I'm terribly sorry I'm asking this question YET AGAIN, but I can almost guarantee that this will be the last time I'll have to ask.
I'm currently on the verge of FINALLY getting these collisions to work for my game, made with libGDX in Java. My collisions use the same method as (and are basically copied and modified code from) the XNA Platformer example (here) where the direction of the collision is based on the rectangle where two objects are overlapping.
The collisions themselves almost work perfectly, but for some reason, holding down/up and left and colliding with the floor/ceiling while doing so doesn't seem to work well. I'm not at all sure why.
Instead of vaguely giving my problem and snippets of code, I've decided to instead provide a binary and the source of the game I have so far so you can see for yourself what my problem is. Link. (Note: make sure you unzip everything into a folder somewhere or it will not work)
You'll find the collision code in the method workingCollisions() in Link.java. Please excuse the messy code and terrible graphics as this whole thing is in pre-pre-alpha.
If anyone is kind enough and helps me out here, you are the best person ever. I'm completely desperate; I've been trying this on and off for months and I just can't get it to work. I cannot thank you enough.