Vaio VGN-FW25G Audio Issues

Hello,

no sounds on my vaio VGN-FW25G after unplugging HMDI cable to TV... strangely all drivers and working perfectly, sounds are OK with head phones. sounds do come back after awhile but they are extremely low on built-in speakers. i've tried reinstalling the
Realtek Audio drivers for my vaio from the sony web page but the problem still there...
plz help