According to reports that shot across the web recently, sources close to both Motorola's Atrix 4G and Droid Bionic said that the devices were suffering from power management issues that resulted in overheating. In addition to the overheating issue, booting and radio performance were also said to be affected, with early speculation that the problem was deemed "unfixable".
Blame for overheating was put on Motorola's choice of PMU (Power Management Unit), with internal sources saying that the issue was already being resolved as these rumors leaked out. To calm this story down, Motorola has officially spoken out saying "there are no overheating issues and the products will ship as scheduled." Both dual core Android devices are set to launch on Verizon and AT&T within months, where I'm sure they'll fly off the shelves problem-free.