You may have to adjust the settings for HDMI. The first time I connected mine to the TV, I had to set the audio output to HDMI, because the default was set to send the video, but audio stayed on the computer speakers. Simple change, if it doesn't do it automatically.
I no longer stream from my computer, I use the PS3 now. I bought a 1TB internet hard drive, and stream video wireless through the Playstation.
2010 335i M Sport Coupe -- Black Sapphire Metallic|Coral Red|Loaded|JB4 Stage 3|BMS DCI|VRSF DPs|Camaross 6k AE|Performance Gloss Black Grilles|CF Performance Spoiler|CF Quad Diffuser|Double Layer Black Chrome Quad Tips|CF Roundels|Smoked Reflectors|Red Cyba Scoops|193s Painted Lamborghini Metallic Dark Gray