Step by step - example: I right click on the desktop for the main menu. Normally just placing the curser over a menu item, say Applications, would activate that item and bring up the next level. I wouldn't click to activate until I reach my target. At the moment however, to open anything requires a left click. If I left-click/drag the curser across text to copy, nothing highlights until I let go of the button. If I right click on a document to open it with an app, I have to keep the right button down so I can click an action with the left button. And when a window is opened, for eg. file manager, I can't move it around on the desktop. If I expand that window then I can't make it smaller, either with the button or by dragging the corner. I have replaced most of the config files with clean backups, but no change.
I am having a bad feeling about VBox. There seem to be issues with Guest Additions - things just don't seem to work right. I am only using it because my testbed 'puter died.