I just had the same problem. For no apparent reason, my touchscreen just stopped functioning completely. All the hard buttons work but touching the screen does absolutely nothing. I opened it up to try the cleaning contacts method of repair. I am no electronics engineer but I can tell you that those are not contacts. That is just a transparent cover over the ribbon cable which is connected at that point but not at the outside. I can only guess that the contact cleaner may have been what fixed the problem.

I do not have any cleaner so I just checked all the ribbon cable connections. At one point I pressed down on the 2 plastic connectors that have ribbons attached at the lower side (on the back) (I had already detached each cable and re-attached to verify good connectivity which did nothing). That seemed to fix my problem. My remote (for now) works perfectly. No eraser cleaning fixed it and I did not clean any contacts.

I don't know if my pressing fixed a cold solder contact, made some other contact better or what but it did work. Now for how long? I can not say.