Sudden, frequent VM crashes.

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I'm running Virtualbox 4.3.40 on Debian 7.11 Wheezy. (I know, it's now out of LTS, and I need to update)

I've got a few machines with very similar configurations:
Debian 7.11 host OS, VB 4.3.40, and one or more Debian 7.11 guests that run various functions.
All of them have been rock solid stable, including this one, until recently.

This particular machine has 2 VMs running, both Debian 7.11, one with an OpenVPN server, and the other with a LAMP stack, along with a bunch of custom Perl scripts.
Just in the past month or so, the LAMP VM has become unstable. The OpenVPN one is still rock solid, and so is the host.
The LAMP VM crashes with an error on the host saying that a critical error has occurred in the VM.

Error dialog

VBox Error.png (73.52 KiB) Viewed 1028 times

The log from one of the crashes is attached.

I've already swapped out the RAM in the host, which hasn't fixed the problem. Worst case scenario, I could reinstall the VM, as the data is backed up, and I have a script to automate the configuration after the base OS is installed, but I didn't want to take the machine down for that long if I could help it.

Thanks in advance,
Chris

Edit: Added the error dialog png, because...surprise...it crashed again.

[CBServices]

So, my original thought was I didn't want to upgrade to Debian 8 until I had the machine stable.

Finally, after no suggestions from the forum (I know...it's a weird problem) I figured I'd bite the bullet and do the upgrade. Worst case, I could reinstall and restore the data.
Anyway, it crashed during the upgrade, but it was far enough along that it tried to boot with the new kernel and some libraries. Into recovery mode, manually start the lvm group and mount partitions, then fix the partially installed packages that were broken.
Finally got the the point I was installing packages that were downloaded but hadn't installed at all, yet. It didn't crash again while doing this, and once I was finished and rebooted, it seems to have fixed the problem. It's been running for almost 3 days straight now, and I'd be lucky to get 6 hours out of it before.
I'm guessing a power failure at some point (it's not on a UPS, but it should be) slightly corrupted the filesystem in a way the journal couldn't recover from, and made it unstable. Maybe the kernel or libc was corrupted, or something similar.

Anyway, TL;DR, the upgrade to Debian 8 appears to have fixed the stability problem.

Chris

Edit: Incidentally, this was the guest OS that I upgraded. The host is still Debian 7, although that's next on my list to take care of.