i got a pair of bluetooth headphone and an imac 2.66 2009 and when i tell it to send audio to them sometimes itunes locks up and last night to computer crashed for the first time since i bought it. i also use plex and when listening i cant get the volume up high enough even after i turn it up in the app ,on the iamc and thehdphones. its a cheap insignia brand but im at work so i dont remember the model #. any ideas?