But let's back up and consider the facts here. First, as best we can tell, the sources are two posters in a HowardForums thread, one of which doesn't even have the information firsthand -- he was allegedly given the news "by someone who is testing the devices." Furthermore, there's really no such thing as an "unfixable" bug; you might need to peel away several layers of software and hardware to fix an issue depending on how fundamental the flaw turns out to be, but engineers have proven time and time again that "unfixable" isn't really in their vocabulary (white paint aside, of course).
None of this really matters, though. The problem -- the reason we're not reporting this as a straight rumor -- is because bugs on unreleased phones, whether they turn out to be real or not, don't matter. This device isn't in your hands, and the manufacturer doesn't intend to let it ship with a fundamental flaw that makes the phone unusable. This holds particularly true for Motorola Mobility, a company that just won its independence and is still in the throes of trying to claw its way back into the big leagues after years of mismanagement -- the Atrix 4G and Droid Bionic are Big Deals for Moto, and the company undoubtedly intends to get them right. Or, at the very least, right "enough" to make you want them.
My frustration is intensified by the fact that neither of these phones have announced ship dates, so -- again, assuming this problem is even real and needs to be solved -- there's not even anything to slip yet! This is why manufacturers and carriers give launch windows measured in quarters, halves or seasons of the year: things are fluid. It depends on how testing goes. There are many, many pieces in the puzzle to get a marvel of modern engineering like a cellphone to ship, and each of those pieces has some wiggle room.
My point? Let's give Motorola (and everyone else) a break. If this was leading to a missed launch date, sure, it'd absolutely be news. If Motorola said "sorry guys, there's a fundamental flaw in these devices and we can't ship them," then yes, we'd be all over it. But a rumor of a bug in a device that Motorola knows isn't ready for consumers -- and has no material effect on any official launch date -- simply doesn't matter.
Update: Good news -- Motorola just dropped us a line to say "that there are no overheating issues and the products will ship as scheduled." Huzzah!