I'm having the exact same problem with a HP Pavillion dv9312eu laptop. (nVidia LAN)
Retrieving Boot.SDI takes approx 20mins (3MB file) and Boot.WIM takes days.
Got both a x64 and x86 image, same behaviour on both.
Other machines grabs the files very quick, one had even deployed the whole Win7 Enterprise in the time the laptop retrieved 40% of Boot.SDI
WMMAYMS / Tobias, got any suggestions?
Edit: WDS runs on Server 2008 R2