CrossOver is an emulation layer for MacOS X and Linux. In contrast to virtualization solutions like VMWare, Parallels or VirtualBox, it allows running thousands of Windows applications, tools and games without having to install a legit Windows operating system.
According to Stellarolla’s blog the upcoming Snow Leopard update 10.6.2 and the Leopard update 10.5.9 will most likely break Intel Atom support. Thus rendering hackintosh installations on netbooks inoperable.
Although Apple does not provide products shipping with Intel Atom CPUs, the Mac OS kernel did support those. Now with the growing amount of hackintoshs it seems Apple tries to stop the use of their operating system on cheap an tiny netbooks.
Probably this is another indicator that Apple is going to bring the long rumored tiny tablet Mac. Anyway for people willing to maintain MacOS on their netbooks the easiest way is to not update to 10.6.2 or 10.5.9 at the moment.