After exhibiting slow performance, or failing to respond, your server records the following in the System Event Log:
Event ID: 2019
Description: The server was unable to allocate from the system nonpaged pool because the Pool was empty.
In addition to the other reasons I have documented for event ID 2019, this problem can occur if you have an Intel network adapter and you do NOT have the latest driver. Previous drivers leaked memory, causing the subject behavior.