Anyway you could record and then upload the sound? It could be a third-party program that's doing it, but without hearing it, it's hard to tell.
I'm also having this issue, it is very annoying. I can only hear it when I try to write/click where I'm not supposed to...is this a feature? can it be turned off?
Tried the Universal Access options but still get the beep...
Had the same problem and found that text to speech had assigned the key I was having problem with to "speak selected text when the key is pressed".
Thanks for the hint.
Also for other users, check if the same issue replicates within different profile.