I signed up to say that I have the very similar or same issue, latest version 2.22 just downloaded from the website, Windows 7x64. I started Defragmentation on D:, it was working fine, after a while I wanted to try to start additional defragmentation on another drive, clicked on it, the GUI switched to that drive but after several seconds stopped responding, I couldn't switch back to D:, as well as click on anything else, the window's just not responding (AppHangB1). But the Task manager shows that Defraggler64.exe still uses CPU and a lot of RAM and the usage changes over time which probably indicates that it's still working? Currently about an hour in this state.
Can I safely stop the defragmentation somehow?
