touch screen won't work after using phone for a while

Hi,

I started this thread a few days ago, but now i'm sure what the problem is.

When I use my iphone, the touch screen suddenly stops working. Mostly after a restart, or when iphone locks after a minute of doing nothing.

If i restore the iphone it works back normal, but after a while it stops back from working.

I tried restoring for a billion times, with the original os, i tried several times with a custom os (jailbroken one),

And it's always the same. (both were ios 4.2.1)

Probably there is something wrong on the logic board i think.

I tried 2 different screens, both same result.

Can i reset the phone on a more effective way than a restore with iTunes?

or does anyone know another solution?

(Sorry for my bad english)