Vista x64 host, vboxsvc.exe quit silently

[digitom]

I had been using VirtualBox on 3 of my PCs (all running Vista x64) happily.

But about one week ago, on 2 of the systems, a few seconds after VirtualBox GUI started, vboxsvc.exe quit silently, and I can do nothing with the VMs any more. If I try to start or edit VM settings, a message box jumps up saying "Failed to open a session for the virtual machine. Callee RC: CO_E_OBJNOTCONNECTED (0x800401FD)".

I don't see any obvious difference of the 3 PCs, all of them run VirtualBox 2.2.2 and have the latest MS updates installed. I also tried uninstall and reinstall VirtualBox on the 2 systems, vboxsvc.exe still quit silently.

Any ideas?

[Perryg]

Have you tried looking at the VBox logs or the Vista event viewer to see what the errors are?
This would help to determine what the problem might be.

[digitom]

Since the VMs can not start at all, there are no logs in the VM folders.
There is nothing about the mysterious VBoxSvc.exe quit in Vista event logs at all.

[Perryg]

Most odd!
Can you determine from the Vista logs what could have changed? Updates.. Programs added, something that will point to what could be the cause?
The only thing that I can think of that may get you back to a working system is to uninstall VBox, reboot Vista, reinstall VBox, reboot Vista, and see if it will come to life.

[vbox4me2]

Open a cmd prompt and run "VBoxManage startvm VMNAME -type gui" to see what kind of message you get.