I just installed build 5029 on XP SP2, and the CSE Validator options are permanently set to 'Irritiating'. The sounds are enabled, and the XP 'tada.wav' is played on success.

This means that, amongst other things, whenever I start/stop debugging, the tada.wav sound is played. This sound is played way too often. It's incredibly annoying.

I've tried setting the options in Tools/Settings/Tools/Tools/CSE Validator/Options, but they have no effect, and when I go back to that dialog, they are set back to the irritating settings. (Enable sounds, Tada.wav/Critical Stop/wav)

I've gone back to build 5020 for now. It's a good job I had the installer lying around, as the 'Previous Versions' link on my product page doesn't work (there are no previous versions stored).

They do have the effect. Probably you forgot to click SAVE button.
Also, you may want to check CSE's registry:
Flags40 in HKCU\Software\AI Internet Solutions\CSE HTML Validator Lite v6\Validator DLL\General
should be 3ff80005

just to let you know, workaround is implemented in 5031 and this build is available for download.

Thanks, I just downloaded the latest version (2011, June) and suddenly, I got a bunch of TADA sounds even when I pressed backspace!!! -- your post helped me solve the prob! Thanks!