You need to return to your Battlenet app and check all those games you have within your list… Click on each one and look to see if the app attempts to update. The error message indicates that the Voice system is missing from your app. So by clicking each game and checking to see if there is an update will correct this.
Another option is to enter your system files and locate the Warcraft folder… from there go through each file which should look like _retail_ _classic_PTR_ etc… once you’ve located each file, search for the UTILS file and open this… it should show you if there is a voice file installed. If not, you will have to isolate the game folder and update.
Personally I don’t mind the error because I’ve actually removed the voice chat system… So if you need the voice chat, you’ll have to view each one of the game files and check the UTILS folder for the voice system.exe
I just started getting this error as well. I have checked my game installation folders and in the UTILS sections I do have the WowVoiceProxy application installed and it was updated today (Feb 1st). So, my error messages started appearing after my game updated