I always have my sound set with "background sound" off, and "sound effects" on. For the last couple of days the sound effects have not been working right after login. In every case I've been able to fix it by toggling the "background sound" on, and back off again, then the sound effects start working. Seems to me like these two settings are affecting each other in a way they shouldn't be, so maybe some of you others could try toggling the "background sound" button to fix it.