Qt Creator在Ubuntu Virtualbox中挂起

I have a very weird problem. Ive got a an Ubuntu 14.04 running on VirtualBox 4.3.20 r96997. I installed QT Creator a while back and was working with it fine until today. Now when I try to start it, the screen is completely unresponsive, and it endes up freezing (just the QT Creator screen, ubuntu keeps working fine)I have a very weird problem. Ive got a an Ubunt