downgrading a virtualbox guest

[berenger.morel@neutralite.org]

Hello.

I made some virtual computers with my desktop computer, which runs a ( 
mostly ) Debian testing. Now, I have noticed that even with virtualbox's 
backports, the computer on which I want to finally use them ( I was too 
lazy to want to learn how to correctly create VMs from command-line ) is 
not able to do so ( in backports: 4.3.12-dfsg-2+deb7u3 and in testing: 
4.3.12-dfsg-1 so I'm quite surprised by this problem. Maybe a wrong 
diagnostic of mine, too...).

So, I tried to downgrade virtualbox, so that on my computer I could 
have the same version as on my target and create anew the VMs. Problem: 
the interface is completely unusable, it says that the max RAM amount is 
0. Trying to create the VMs in command-line and then opening the 
interface, still no luck.

Do anyone have any idea, or will I have to upgrade the distant computer 
to testing ( virtual box depends on a newer libc, so I'm not really fond 
of it )?