I'm experiencing frequent freezes of the host Linux OS (not the Parallels app, apparently) using Parallels 6.0.12090 rev. 660720. It seems to be related to unplugging the USB wifi adapter. It doesn't happen every time, but often, and it *seems* to occur only when the mini-USB end is unplugged accidentally. This was not a problem in prior PD6 versions using the exact same VM. The only difference is the PD6 version and the tools which were compiled for 2.6.38. Again, PD6 doesn't freeze, but Linux does. I'm not sure how to get any debugging info. It doesn't crash—just locks up. I don't think it happens (at least as often) when the USB-A plug is removed. I have many cables and made sure that wasn't the source of the problem. My current work-around is to TRY to keep the devices attached, but it isn't easy given my mobile setup.
