I have no idea why this happens, but it happens WAY too often. I'll be running the server for awhile, sometimes 10 minutes or 2 hours, and I'll get this cryptic error message in the console:
"Error sending outgoing packets: No Error"
It usually pops up about 100 times in a row too, followed by:
"Disconnected from Master Server"
This is crazy. I'll be in a game and never know it even happened. The game doesn't lag, I just suddenly notice that the server is dwindling down on players and no one new is coming in and check the console and sure enough, every time, this is what I see. Why doesn't the darn server even try to reconnect after that?
Any advice or commiseration would be appreciated.

Huh. That is odd. It hasn't occurred to my server, yet at least. Though I do get the occasional "Disconnected from Master Server", at which point I re-launch the server, and from there it works stable enough.

My advice is next to naught in effect, perhaps. Albeit, perchance a couple of restarts, and check your IPv4 - mine changes now and then at a variable rate.

I can't tell you how many times I've restarted the server, both the console and the physical machine. It can't be (just) an IP change because it can happen several times a day, and I don't lose my Internet connection that often.
If this bloody server would timestamp events I could check my router logs and see if anything suspicious was happening then, but I never catch it until long after the fact.

From what little I can tell, I understand it is a bug or glitch in the Operating System. It could be your firewall is acting up as not intended. That, or there may be signal interference within the router's vicinity.

Are you using pyspades or the official Ace of Spades setup?

No firewall. This is running on Win2k3 server.
I'm running the official vanilla server until pyspades becomes more stable. >.>

In this case, I recommend deploying the official (Yes default, but more reliable) Ace of Spades server. My recommendation comes weak-backed, but there is almost no negative issue with the default server setup, in which prerequisites the server to function at all.

Did you try to restore the server files or software?

That is what I'm running. The official server. Vanilla meaning no modifications to it.

Well, no one else has responded to this thread. This makes me sad. T_T
I'm still getting the error and frequently. I got the error less than 10 minutes after launching the server once. Mostly, though, it takes several hours to half a day for it to happen again.
Here's a screen shot of it happening. If I scrolled up in the console, it'd show that one blasted line as far back as the console logs.

http://dl.dropbox.com/u/1129844/AoS%20Error.png

Any other ideas? I see that Pyspades released a new Windows binary yesterday, I might just do that...