I have the latest BootCamp as far as I know, the 4.0 version. Anyway everything works fine with me, except the sound, I have reinstalled the Realtek several times and no success. I would like to know an way to solve this problem, thanks!
I only used the CD first time to install the drivers, after I noticed there was no sound on my system, I started to look for any solved cases, and then find about the Realtek newer drivers and etc. And I'm using Mac Mini i7, with Lion Server.
Did you run Windows Update? That might update the drivers properly. Other thing to check is that the output device is selected in the driver. Speaker, optical, mini-jack, or LED Cinema Display.