From Jayski.com:

Mystery surrounding loose lug nuts at Charlotte: UPDATE more info: During the race broadcast, SPEEDtv analyst, Ray Dunlap reported that the #18-Kyle Busch Motorsports team found eleven lug nuts loose on three wheels just prior to race start. On Lap 10, #3-Austin Dillon suddenly broke loose, veered right and hit the wall. It was later found that there were loose lug nuts on the left-rear of the #3-RCR truck.(5-22-2010)
UPDATE: There was also concern before and early in the race about at least two trucks -- including Busch's -- that mysteriously had loose lug nuts. "They just found that three of the wheels were loose," Busch crew chief Eric Phillips said before the green flag. "We've just got to keep a better eye on our stuff, I guess." Phillips refused to speculate if he thought someone intentionally loosened the wheels. But 20-year-old Austin Dillon -- whose car was parked behind Busch's in the impound area after qualifying -- claimed his wreck on the 10th lap was caused by the same problem. "They left the left-rear lugs loose. We don't know what happened," said Dillon, grandson of NASCAR team owner Richard Childress. A NASCAR official said they were looking into the matter.(ESPN/AP)(5-22-2010)