Suddenly can't add virtual servers

I recently installed virtualmin and managed to create a virtual server and everything worked fine.
But today, I tried to create a new virtual server and I get this:

Creating administration group hundred …
… done
Creating administration user hundred …
… done

Failed to create virtual server : blank

For some reason, the actual error is blank and so I have no idea what has happened and what I have broken since I added the previous virtual server.

Any Ideas?


I have just solved it somehow - I restarted the VPS and it miraculously started working again.