Will downgrading from os x 10.7 fix audio problem (no sound at headphone port)?

I have an older black Macbook (2007, 2.16 GHz Core 2 Duo processor, 4 GB SDRAM) that's been upgraded professionally with SD drive running OSX 10.7.5. A few months ago while watching a movie using headphones, I lost sound, mid movie. Since then, whenever I begin listing to something with headphones (or attach my stereo to laptop via headphone port) the sound cuts out within 2 minutes. I've fiddled around with audio parameters according to advice elsewhere here, but nothing returns the sound. I'm reading some people have problems with Lion and their audio systems. Has anyone else had this problem, downgraded from Lion, and found the problem fixed?