In Apple's latest round of software and hardware releases, the second-generation Apple TV got a software update to add more features for HDMI support, AirPlay, and surround sound for Netflix movies; however, along with the update a number of people found their televisions began flickering, especially if they were using HDMI to DVI adapters.
More recently, Apple's updated line of MacBook Pro systems has encountered a problem profiled on MacRumors and discussed in great length on this Apple Discussion Board thread, where the systems have been locking up when under heavy load. While the machines appear to be running, the input to them seems to be frozen so users cannot do anything, and end up forcing the systems to restart.
These machines have new hardware in them, including four-core CPUs and brand-new Thunderbolt I/O technology, and it is possible there could be a bug in the firmware or software drivers for these new features, which may lead to the problem. The same goes for the Apple TV problems, which are clearly a software issue because they started happening with the latest updates.
In both situations, Apple representatives have said that they are aware of the issue and are working on a fix, which should come in the form of a software update in the near future. In the meantime if you are experiencing problems with these new machines you might consider trying some potential workarounds.
For the Apple TV, you can try an alternate connection to your television if you use a DVI-to-HTMI adapter, but this seems to be the only fix that has worked for people so far.
For the new MacBook Pro, the problem is likely in the display drivers, since most of the crashes are happening when people enable graphics options in various programs or use graphically intensive applications such as games or CAD software. In these cases you might try booting and running your system in Safe Mode (hold Shift at start-up) to see if that allows it to run without the potential for crashing. Additionally, you can try reducing the graphics settings in the programs you're using to see if that helps the problem.
In terms of the graphics in the new systems, there could be an problem either with the use of the discrete graphics card or with the switching technologies. Either way, you might try testing the problem by installing "gfxCardStatus," which is a tool that can force the system to use only one GPU and thereby prevent automatic switching or the use of one GPU. Try different GPU setups with this tool to see if you can prevent the problem from happening.
Lastly, one option you might try is to format the hard drive and reinstall the operating system. Even though the issue is being tackled by Apple's engineers, in the past some problems have happened because of faulty initial installs, and have been fixed by reinstalling the operating system.
Regardless of what you do, be sure you make regular backups of your data to avoid losing any of your work, and lets hope Apple issues a fix soon. It looks like the engineers are working hard to do so.
UPDATE: Apple has released OS X 10.6.7, which addresses this graphics bug in the new 2011 MacBook Pro systems. The update should be available through Software Update, but can also be downloaded as a manual update from this Web page. Be sure to fully back up your system before applying this update.