thanks a lot! The battery may have been the problem. The BIOS-settings had been changed. I changed them again an everything is OK.
Thanks for the quick answers.
Today I say the following error, while I was trying to start a virtual machine.
Here is the error code:
Error while powering on: This host supports Intel VT-x, but Intel VT-x is disabled.
Intel VT-x might be disabled if it has been disabled in the BIOS/firmware settings or the host has not...