Nintendo of Europe issued a statement to Eurogamer suggesting that this issue could be fixed by downloading the latest firmware. If that doesn't fix the issue, the company recommends users "contact their local Nintendo Customer Service centre to investigate the problem further."
Some users are also reporting an excessively loose hinge, causing the top half of the system to wobble during play. "The hinge i thought was OK," reports 3DSBuzz forum user Suspiria, "but throughout the day it has got worse and worse." Nintendo acknowledges the possibility of such an issue on its support site, advising those who suffer from it to send the system in for repairs. We're contacting Nintendo about both issues, and will let you know what shakes out. Hopefully, it's not the top of a 3DS.
Update: Nintendo sent Joystiq a statement asserting that "The number of calls and emails received by our customer support center is well below the rate experienced during past hardware launches, and there are no widespread issues." Find the full statement after the break.
"U.S. day-one sales numbers for Nintendo 3DS were the highest of any Nintendo hand-held system in our history. The number of calls and emails received by our customer support center is well below the rate experienced during past hardware launches, and there are no widespread issues. As always, people who have questions or comments about Nintendo 3DS or any Nintendo products can visit our support website at http://support.nintendo.com or call 800-255-3700."- Nintendo of America