I was doing an overnight render and woke up to see that houdini had shut itself down. I try to start it up again, thinking that maybe the machine had crashed and restarted and now I get this error upon launch:

ERROR: invalid machine name

The license server is not running
The license server may not serve licenses
The license server does not allow this machine to read licenses

The option to manually enter the keys is greyed out, so I'm stuck.

Any ideas as to what happened, or how I can get houdini running again?

UPDATE: a restart seems to have fixed it - I'll see if it's still running when I get home tonight.