A while ago I"ve faced with a problem on VPS - there were no free space! I couldn't login into admin panel installed there. SSH was not working too.
The only thing that was wroking was FTP server which helped me to connect and free some space deleting non used files. After that operation I've finally logged in.
So, be patient to the free space available on your server and have a couple of entrances there.
One of the solution to prevent the situation like this is to have a dummy file which can be deleted in such critical moments to free up the space.