I had a complete system hang while I had Sandboxie running - it wasn't actually anything to do with Sandboxie, a NES Emulator I was running was lagging a bit so I gave the process real time priority. Couldn't do anything afterwards and had to do a hard shut down. Vulcan nerve pinch didn't even work. On boot up, the system spent a long time getting rid of references to files in C:\Sandbox. Clearly giving a process real time priority wasn't the best idea, but there are a number of other things that can cause similar crashes, and if you're in a hurry to reboot, Sandboxie's gonna cause some problems. I like the idea, it has some decent benefits, such as being able to terminate programs inside the sandbox easier than through the task manager, but the cleanup necessary when it couldn't shut down properly is quite a pain. In my case it took at least 2 hours for the file system to get cleared up - that's after running my system without shutting down for over a week.