When did that problem start?
What did you do right before that problem appeared?
You said stock roms, does it mean its same on stock based rom or on clean stock rom, like after you do repair software with pc companion?
Is your phone SIM locked, meaning locked on one network? Wad i locked before and you unlocked it?
Type *#*#73784236#*# in dial pad and go to servce info->configuration, what does it says: under rooting status?
P.s.: in future use Q&A section for questions. While posting this you even answered/mark that its a question