I installed VirtualBox on my Fedora 21 but every time I open a machine my note hangs completely [closed]

After many problems I was able to install VirtualBox in its latest version in Fedora21 also with its latest version of the kernel, but when I open a virtual machine, my note hangs completely and only goes on and on again to return to life. My note is a Dell Latitude 7350, 64-bit, with 8GB of RAM, 500GB of HD, Intel Core M-5Y71 CPU @ 1.20GHz x 4. That is, by note type was not to give this problem. What could it be?