Running a guest system in VirtualBox. Host is Linux Mint 15 KDE.
Can't use Alt+drag to move windows or easystroke mouse gestures in vm because host steals the mouse. I can see because guest and host have different cursors. Someone on a virtual box forum says it's the DE that catches it and you've gotta adjust the DE behavior.
How do I let guest to catch alt clicks and right-click drags so I can work in a functionnal environment?

It sounds like the Oxygen style might be causing this issue.
Can you try starting VirtualBox with the argument "-style plastique" to see if that has an impact?