When you say "I cleaned it", did you take the remote apart? Some dirt could be applying constant pressure on some part of the screen, which could explain the erratic behaviour and the "self starting" which you had in the beginning. I had this problem some year ago and my Pronto is still working today after the cleaning from the inside.

I therefore recommend you to take it apart and clean especially the rim where screen and body touch.
There are some threads regarding this and also on how to take the Pronto apart (3 torx screws- get the screwdriver from any hardware store. Beware: one of the 3 screws is hidden under the serialnr sticker.
If you're new to this check these great description
[Link: joey6p.com]
(each bullet is also a link to pictures which make the operation easy for any newbe)

cheers