Virtual network is gone from a VM

Hi,

I have a VM that suddenly has lost it's virtual network. When i choose configure, the virtual network section is missing. The virtual network is still there and used by other machines, but this VM just lost it's network. How can that happen??? And how can I fix it? This happened today when I restarted the VM. 

PS: Yes, I'm 100% sure the VM was created on the virtual network in question.

brgds