I looked for a lot of articles regarding my problem, but none of them seem to explain this particular behavior. I have a Windows Server 2008 R2 SP1 installed as a host OS and a Hyper-V role enabled. I have 4 virtual machines, which were working like a charm until yesterday. The core environment didn't change, everything was working well, but at one moment all VMs stop working. When I try to start any of them (or new one created) it says: 'machine' could not initialize. Where the 'machine' is a VM name.
NOTE: they were working on this host without any issues. They were working, they were started. The machine was not rebooted and nothing was installed there. They just stopped working at one moment.
I checked BIOS - the Intel Hardware Virtualization is enabled. The test tool shows that the Hardware D.E.P is enabled.
UPDATE: The machine was rebooted after BSOD.