Originally Posted by DCB0

... or perhaps a spoke was damaged somehow.

Is is possible that the wheel was laced to the spokes are in the wrong-offsetted hole in the rim (ie the ND side spokes cross over to the DS of the rim and vise versa)? I accidentally built a wheel like that many years ago, left it like that because I was lazy, and spokes started popping like mad after not too long. I cannot remember if they were breaking at the nipple or at the elbow, but I recall being surprised at the way they were breaking... so it is likely it was at the nipple because most spokes break at the elbow.Nope.Laced properly all around.

edit:
If the wheel is laced wrong then correcting this will give you and extra mm or two of length to use to correctly tension the wheel!