They're Vuelta hubs, on Aeromax rims.

This morning I tried taking them apart and loosening them up, and it seems to have solved the problem. Thanks!

Here's another question though, just for understanding's sake. How is the pressure on the bearing from being overtightened different from the pressure that's place on them when a rider is on the bike? Do the bearings roll better under their intended load than when the are too tight?