it normal I had this since I switch from Treos (on palm os )all my windows phones did that ( 700w x2, mogule x4, tp x5, tp2 x1 = total 12 phones
)
I tried to do hard resets, cooked roms, tweaks, etc. nothing help.
Looks like it happens when there is change in signal strength. Could be just change of few bars and it doesn't have to go to x1. You have to learn to live with it. Sometimes is just pisses me off when accidentally my phones dials numbers when woke up while in my pocket.
so ppl dont speculate on what it could be - there are numerous posts on xda,ppc,treocentral forums about this issue ( some of them are even made by mua).
peace my good ppl