guest VMs stop unexpectedly

[dream]

Hi All

I'm new to VirtualBox. I just switched from VMware to VBox.

I created 6 VMs using VMware vmdk files and VBoxManage clonehd --format VDI.
5 of 6 VMs are Windows 2000, and the last is Debian 6.

In all Windows guests, I changed to "Standard PC" instead of "ACPI PC".
Nested Paging are all enabled. IO APIC all disabled.
Guest addition are all installed. And I carefully turn off "power management" in all guests.
memory are 512, 512, 512, 512, 768, 1024MB.

The host is Debian 7 64bit on a dual L5420 IBM x3650 server with 8GB memory.
VBox installed using stock Debian package 4.1.18. ExtPack installed.

I used Xfce and started VirtualBox from menu. Everything runs fine after migrating.
Then I put all VMs into headless mode.

The problem started to appear. 4 Win and the Debian VMs stopped unexpectedly. All of them (five) seemed to stop at the same time.
Today it happened twice. It's strange that one Win VM never goes down.

In Windows Event Log, the system unexpectedly shutdown.

Any idea will be appreciated.

[noteirak]

Please read Minimum information needed for assistance and provide the VM log of the last VM you started before the crash.

[dream]

I'm sorry that I forget the exact VM I started last.

log files check attachment

win-fine-Vbox.log is the one that didn't stop.

[dream]

I'm not sure about which log files may help. The attachment is all log files in Log directory of the Debian guest.

[mpack]

The log files in the Logs subfolder are from the most recent 4 sessions. VBox.log is the most recent session, the .1 file is the session before that, .2 is the session before that, etc. We only need one log file, from the session that exhibited the problem.

[dream]

The log files in the Logs subfolder are from the most recent 4 sessions. VBox.log is the most recent session, the .1 file is the session before that, .2 is the session before that, etc. We only need one log file, from the session that exhibited the problem.

Thank you for reply.
Actually, I am not very sure I correctly identify the log in question. So I packed all log files in Log directory of one VM.

[noteirak]

Well, pretty impossible to know for sure whihc one it is.
Regarldess, you have 8 GB of RAM, but run 5 VM on top of your OS. My bets are on you running out of RAM.

[dream]

Well, pretty impossible to know for sure whihc one it is.
Regarldess, you have 8 GB of RAM, but run 5 VM on top of your OS. My bets are on you running out of RAM.

6 VMs have 512, 512, 512, 512, 768, 1024 MB.

24 hours ago I started VMs by VirtualBox GUI, ie. not Headless. Since that no unexpected stop occurs.

[noteirak]

so you're at 4GB, if you take into accouht the VRam, and more if you add the Virtualization overhead. Add your host OS + your applications, seems borderline to me.
Especially since Windows will kill applications on its own if you start being RAM starved.