Parallels released beta3 of their Virtual Machine for MacOSX today. I installed it immediately and all my earlier problems were solved. Networking works perfectly, no more crashes or kernel panics, no more cpu usage during idle time, and best of all ... it's fast as hell!
One of RIFE's test suites that takes 117 seconds to run on the console in MacOSX, took 124 seconds in Ubuntu Linux inside Parallels. That's almost exactly as fast!
I'm taking out my credit card right now to pre-order Parallels Workstation for MacOSX. This is the greatest virtualization technology that I've ever seen.