Been fooling with this for a while, finally got it narrowed down enough to where I can reproduce it on my Macbook Pro and thought it might be worth posting. Issue: Upon resuming from OS X "deep sleep", Parallels desktop running a Windows XP session will throw up 3 dialog boxes about connecting the USB HID devices and iSight camera to the virtual machine. Until these dialog boxes are dismissed, Parallels will consume 100% CPU. Once the dialogs are dismissed the CPU usage goes back down to normal. To reproduce: Start up a Windows XP session in parallels. On the OS X side, put the system to "deep sleep" mode where the session is written to disk, like Windows XP hibernate mode. (you can achieve the same result by unplugging the power adapter on a notebook, and allowing the power to go to 0%. OS X will automatically put the system in deep sleep mode to protect your data.) When the system is fully off, hit the power button to resume.