I recently upgraded to patch 1.05b. I went through all three patches, 1.03, 1.04 and then 1.05b.

I started the game...no problem, played for a short bit and then I lost sound....Anyone else experience this problem?

I'm tempted to go back to the original version, sound is critical when playing this game.

I've had the same problem. Mine was caused by a conflict between the updates and my soundcard. Since I had that problem with some other games, I changed my soundcard and now it works just fine.
P.S.: I had a 128bit genius soundcard, now I have a 128bit Soundblaster Live.