A problem? Not a terrible one, but as you can see from the chart over there, there is a definite downturn in new Mac shipments. That might actually be good news for Apple, though -- with the economy doing a nice downturn lately, less inventory might shore up sales a bit, and keep their budgets in line with estimations. Of course it would also mean fewer Mac sales (and despite the recent popularity of the iPhone and the iPod, Macs still make up the majority of Apple's revenue), but if customers aren't there, that's better than having warehouses full of computers paid for but not actually sold.
It's definitely not a sign that the company is going down in flames (in fact, all evidence says exactly the opposite), but it may be a sign that Apple's amazing growth is slowing down a bit.
Thanks, Larry T!