After uninstalling some old software and updating some other software, after a reboot I was greeted with a VERY long login process.
When Windows finally did log me in, besides Gadgets not loading and no working Internet connection, this message popped up in the system tray:
Failed to connect to a windows service
Windows could not connect to the System Event Notification Service service. This problem prevents standard users from logging on to the system.
As an administrative user, you can review the System Event Log for details about why the service didn't respond.
Well, what a load of crap.
From the lowercase spelling of "Windows", the "Service service" part, and the fact that the System Event Notification service failing to load PREVENTS you from even viewing the System Event Log, this is a pretty useless error message.
Open an elevated Command Prompt, type netsh and hit Enter, type winsock reset and hit Enter, and then restart your computer.
After a reboot, Windows logged me right in and everything seemed to work.
I'm guessing the cause was me removing the latest VMware Player. Maybe the removal of its networking components broke something.
This may apply to Windows Vista and Windows 7 only.