Sony Vaio very slow streaming

I have a Sony Vaio, 2.2ghz  x2 core AMD , 3 gb ram,  i can watch dvd,s , you tube , online movies on no problem,  , BUT ,   if i stream say  .mkv from my WDlive plus , the video  stutters and loses sound ,

This is the same for wifi connection and cat5e direct cable !!!

My main desktop pc is fine,

I am at a loss as to why ? 

I have also tried VLC as an alternative to Mplayer , but its much the same !!

Any advice be great ,

thx

Maybe you should try contacting WD’s Technical Support about this. You can do so either by phone or email.

To Contact WD for Technical Support
http://support.wdc.com/contact/index.asp?lang=en