Strange error: failed to load unit 'pgm'

[SpeedRacer]

I'm trying to wake up a VM from a snapshot (state: turned-on) and all of a sudden I get this error:

VBox_error.gif (17.45 KiB) Viewed 2971 times

Anyone has any idea what does it mean?
Thanks in advance.

[Perryg]

There is a difference in the saved state and the now state. You can post the complete log file ( as an attachment ) but in the end you will need to discard the saved state.

Things to check:
Host drive ( is it full )
Host drive for corruption.

[SpeedRacer]

Thanks for taking the time to look Perry.

Absolutely no chance of "disk full" (either VDI or host's) so looks more to the corruption side.
The referred "shot" is shot #7 in a cascade of progressive shots. Previous shot (#6) is the same but before turning on the VM, so it's an "OFF" state shot, when restored, it BSOD's. I've gone as far as restoring shot #1 (OFF state) and BSODs too, so the corruption should be in the first {xxxxxxxxxx}.vdi of the chain.
When I boot from an external disk and "view" the supposedly corrupted disk, the files are there. I can copy/move them, etc.

So any chance of doing something about it? It's an important image and I have no backup. It's not about data, it's the "system" which is important, which contains many programs configured in specific ways.