I am having a button problem too so I opened my Pronto to figure out what was going on.

Here's what I found out. Under the hard buttons there's a thin rubber pad with dimples containing some kind of small metal(I think) disc. When a buttun is pressed the disc makes contact with a circuit board and completes an electrical circuit for that button's control. The way the disc is implanted in the bubber makes it like a spring so that when you stop pressing the button, the disc pops back up.

What's happenend, at least with mine, is that the rubber around the disc has torn from repetitve use and now ths "spring action" is gone. That's the only button that's giving me a problem.

If the problem is with all the buttons, it could be that this rubber pad is not seated correctly under the buttons or the connection between the button curcuit board and the rest of the Pronto is loose.

I'm not a professional so these are just my personal ideas and thoughts