There is a bug in 1.6.1 that leads to such behavior, if you try to open a file with special characters, e.g., parentheses () in its file name or path. Please try to rename the archive and open it again. Does this solve the problem? That cancel doesn't really cancel will also be fixed in the next version.

By the way: You can hold down the Option key while right-clicking any running application in the dock. The context menu will now contain Force Quit instead of Quit.