There's three known workarounds for this.
If you're in Vista, setting the compatibility mode to XP SP2 worked for me. To do that, right click your CoDWaW.exe in C:\Program Files (x86)\Activision\Call of Duty - World at War (No (x86) if you're in a 32-bit system. Change the drive as necessary, of course.) and then go to Properties -> Compatibility, check the "Run this program in compatibility mode for:" box and then select "Windows XP Service Pack 2" from the dropdown menu, hit apply, then give it a shot.
A more common solution is to go to Control Panel -> Phone & Modem Options -> Modems and then to disable any modems you're not using. This didn't work for me, since I didn't have any modems set up. This seems to work for anyone who has extra modems set up.
The final workaround is to go to Control Panel -> Sound and right click your main sound device (e.g. 'speakers') and go to Properties -> Advanced then select '24 bit, xxxxx Hz (Studio Quality)' (The x's can be any number, so long as the rest is the same.) this one tends to work for those who don't already have their sound set to this. I, however, don't have 24 bit sound available for my setup, so this didn't work for me personally.
Hope you get it running, pretty good game.
