virtualbox.org

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?

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.

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.

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.

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