please help me pbm in k790i

frnds please help me. i have a screen hang problem in my newly bought sony k790i. the pbm is dat the screen turns blank as i speak for a long duration continuosly but my call is not interrupted. but once i cut the call i m not able to see the normal standby screen and neither am i able to navigate to menus or switch off the mobile.i ve to remove and re insert battery for further use . i reported this to one of the authorised service centre. he said he ll look into it and when i went back to get the mobile he told me has changed antenna speaker box in da set. now wht confuses me is that i don knw wht does an antenna do with a screen hang and what is antenna speaker box? does they have an effect on screen freeze poblem. please help me.. its a hard earned money of 10k tht i bought this mobile. please help

if reflashing hasnt sorted it it has nothing to do with the antenna k790 have a bad problem were they freze at the logo or after some time off being turned on it needs to go to sony to be fixed :( as it is 2 ics near the camra that have to be changed take it back if u have only just borught it and say u want a replacement