This sounds very similar to the problems that others have been experiencing. Right after it came out of beta I had a this problem also. What I did was to uninstall using SDC, including any sound packages that I may have downloaded. Reboot and install again using SDC. I'm not sure if it wants you to reboot again after you reinstall. Give it a try. I will tell that for some folks this doesn't do anything, it did work for me. Come back and post whether it worked or not.
