I was moving my computers around this weekend and screwed up the connections. I slowly got the network back up, but the file server stumped me. I spent hours trying to get it back on, but finally gave up last night and went to bed. This morning I started to gather some information to post here for some advice and saw that something was different. Sure enough, it was back on! It’s like invisible penguins came overnight to do their magic.
You were probably so tired and frustrated, that you missed something easy and obvious. This morning, refreshed by a good sleep, you did that step that was simple and obvious. And it was so simple and obvious, you did it without even noticing that you did it.
Just guessing. But what I just described does happen.
I don’t remember what I last did. It might have been to switch to init 5 to see if I had better luck with the tools there, but I ended up getting a blank screen. So there might be a script there that does it automagically. I noticed that the IP address had changed this morning. Whatever, it’s good to be back up and running.
Depending on the services the server runs, it could have been simply timing out, waiting for network devices to become ready. Now that you waited to get it to runlevel 5, you outwaited the time outs ???
Mind, on a server it’s best to set the network devices to start at boot, not at cable connection. I’ve seen quite some NFS, NIS and Sambe issues related to this.
Aww! I really wanted it to be the penquins!
We can believe, can’t we? 
I believe! I believe!
All hail the Penguin!