Linux Guest Freezes After Pressing Ctrl-Alt-Delete

[xthx1138]

VirtualBox Version is 4.3.12, including latest Guest Additions
Host is Win7 Ultimate SP1
Guest is Debian wheezy

The guest is freezing (or becoming nearly unresponsive -- let's call it a very hard frost) after I press Ctrl-Alt-Delete on the host. I frequently do this to lock my workstation while I'm away, but even if I just press Ctrl-Alt-Delete and then press "Cancel" right away to return to Windows, I see that the guest has gone into this unresponsive state. According to Windows Task Manager the CPU and memory are not taxed at all, and no other application on the host appears to be slowed.

My reaction is to just power off the guest and start it again. I'm not sure what log files to collect or where to begin troubleshooting a freeze like this.

[noteirak]

This post will tell you the required infos we need to help you out.

[xthx1138]

I've attached the guest log. I started the guest, logged into it, then hit Ctrl-Alt-Delete to get to the Windows page for locking the workstation, then hit "Cancel" right away to return to Windows, and then immediately the Guest was frozen. That's when I saved off this log.

Also, some confirmation/clarification of other details:

Host: Win7 Ultimate 64-bit, SP1
Guest: Debian wheezy 64-bit
VBox Version: 4.3.12 r93733, Including latest Guest Additions