Windows 7 logs out completely when RDP session is disconnected

I have a Windows 7 PC that I RDP into when I work remotely. I'm having an issue where this machine logs me out completely whenever I end the RDP session. I am not initiating a logoff. This happens when I click the "X" in the remote desktop bar, or if I lose the network connection for some reason. The next time I RDP back into it, or log in from the console, I get a completely new session. This is particularly annoying when I have a shaky internet connection and I have to run something that takes a few hours to complete.

I have checked the Event Viewer to see if there's anything that looks unusual, but I might not know what I'm looking for, even if I see it. The only event that I see that is close to the time of logoff is an actual Logoff event in the Security sub-section of the Windows Logs section:

An account was logged off.

Subject:
    Security ID:        domain\username
    Account Name:       username
    Account Domain:     domain
    Logon ID:       0x1377093d6

Logon Type:         3

This event is generated when a logon session is destroyed. It may be positively correlated with a logon event using the Logon ID value. Logon IDs are only unique between reboots on the same computer.

I checked the Group Policy (under Administrative Templates\Windows Components\Remote Desktop Services\Remote Desktop Session Host\Session Time Limits) to see if there was a timeout set for inactive sessions, and I experimented with changing the values of these settings, but nothing seems to affect it.