I have very similar issues. I have an Apple Cinema display with a keyboard attached that I connect in the morning. On occasion (about once a week, or more), the keyboard doesn't work. Sometimes I see the Parallels prompt to choose how to use the USB device (which doesn't respond and is frozen), and sometimes switching to the other USB port solves the issue. Most of the time I am forced to perform a hard reset of my MacBook Pro. It seems something very deep in the kernel gets "stuck". I actually missed an important email this morning as a result of the time it takes to deal with this issue. I hope they fix it soon.
Setup:
MacBook Pro 15" (No retina, i7, 16GB RAM)
Latest Parallels (updated yesterday)
OSX 10.7.5
Guest: Windows 8
Last edited: Jun 28, 2013