VirtualBox Manager GUI hangs after removing virtual machines

[m6477]

VirtualBox Manager GUI (VirtualBox.exe on Windows host) hangs after removing virtual machine(s). Typically this happens after closing a virtual machine and then removing that virtual machine. I managed to reproduce it a couple of times thus:

1. Start VirtualBox.exe
2. Create linked clone 1 from existing powered off VM, without reinitalising MAC address
3. Create linked clone 2 from existing powered off VM, without reinitalising MAC address
4. Start clone 1
5. Close VM, saving the machine state
6. Start clone 2
7. Close VM, saving the machine state
8. Remove clone 1, deleting all files
9. Remove clone 2, deleting all files

At that point VirtualBox Manager hangs, Task Manager says it's running at CPU 13% (on a host with 8 logical processors)

The VM directories and files do get deleted, and if I kill VirtualBox.exe and VBoxSVC.exe from Task Manager, or logoff/on, when I restart VirtualBox everything is fine (the VMs have been removed).

It also hung if I shut down the VMs (start button, shutdown in the guest) instead closing the window on the host. Attached are two sets of log files, one for close and save state, one for shutdown.

The VM directories do get deleted, so I can't get VBox.log from the VM to send.

The problem happens on two different host machines, both Windows 7 SP1 64-bit. Usually my guests are also Windows 7 SP1 64-bit, but I also reproduced the problem (same steps as listed above) on a Win7 host with two linked clones of Ubuntu 12.04 64-bit.

The problem is not new to VirtualBox 4.3.18 - I have experienced it in earlier versions (eg 4.3.12)

[aeichner]

Please reopen if still relevant with a recent VirtualBox release.