The last time I had that happen on a wheel, I checked the spoke-tension (the wheel wasn't built by me). It was up and over 200kgf. I don't know why anyone would do that. The nipples were brass. The wheel had been handbuilt by the LBS that ripped me off and hadn't done the work I paid 'em for. So I wrote it off to "Typical."
So I suggest you find the spoke-tension on this wheel. You don't want to ride on a wheel with double the standard tension.