I recently found this issue in two of my home PCs.
All sounds, including system sounds, play normally with the exception of system sounds related to dialog windows, i.e. Asterisk, Critical Stop, Defalt Beep and Exclamation.
So far, I've ruled out problems with sound drivers and / or related configurations, as one of the affected machines uses a Sound Blaster X-Fi sound card with official drivers and the other uses onboard sound. Also ruled out corruption and integrity problems with system files by running System File Checker.
I've also checked the sound cpl and everything seems okay. In the "Sounds" tab, all the sounds play when clicking on "Test", even the affected ones. In the registry, all the mentioned sounds are correctly associated with the respective events in AppEvents, for all schemes. It happens with all the sound schemes, thus it's not a problem there either. New user accounts are also affected by the problem.
That had me thinking that it was something to do with a misconfiguration on my part, however, as referred, it only happened on two of my PCs, and only recently.
Does anyone have this problem or can help me solve it / troubleshoot it? I really don't know what's going on.