Going to the bathroom in the wrong corner

When I moved into my new apartment about 6 weeks ago I had no problem with him using the only corning really available in my bedroom. I use puppy pee pads not a litter box as I had a hard time getting him to go in a box and I find this much easier to clean up. Anyway about a week or so ago he started using another corner. Now, this would not be an issue as I could have just switched his corner to that one but that corner happens to be the one in front of my door. My door is always kept shut when he is out of his cage, I have a roommate who isn't the biggest fan of him so I can't let him out of my room really. I've tried a couple of things. I cleaned the area with a lemon scented all purpose cleaner so it wouldn't smell like it, thinking this would deter him from going in the corner, no luck. He sometimes goes in the other corner so he knows that is a bathroom corner, so no need to move his feces to the proper corner. I tried a spray that is a mix of vinegar and water and sprayed that there as well. Still no help. I've put a small plastic storage bin in the corner and he just goes around it. I've also tried putting food in the corner. Still goes there. I'm at a complete loss on what to do. This is a very big problem and I can't just restrict him to his cage. While his cage is quite large, as you guys know they need their freedom. I also have a small cat and they love to play together. A whole other problem in relation to the cat is when he goes to the bathroom on the pee pad his instinct tells him he needs to cover it up, since that is what cats do with their own, and so she does her best to turn over the puppy pad and cover it up! So yeah any help would be greatly appreciated on the first matter at least.

Wow, I can only imagine...
Can you cut down a side of a litter box so he can get in and out easier?  I know it's tougher to get a ferret to use a box out of the cage.  
Do you have a box in he cage, and does he use it?  Best case would be to get ferret and kat to use same box.  It worked once for me years ago, but I was using clay litter.

THE DOOKS OF HAZARD

> I use puppy pee pads not a litter box as I had a hard time getting him to go in a box and I find this much easier to clean up.