Navigate to your Steam - Clear Download Cache The Steam library folder contains all of your installed games on disk.
Restarting the computer flushes all kinds of system states and caches, while resetting other programs and releasing locks on files and other resources.
Clearing the Steam download cache will cause the Steam client to flush locally cached configuration data and acquire it from the Steam servers again.
Steam sometimes requires administrative privileges to update itself.
If it doesn’t have these permissions, it gets stuck at a specific point.
Open up the developer console and type: "runtime verification: 0" and press Enter.
This will prevent the update script from running and skip to starting Steam straight away.
The specific reason for the error will be shown in the parenthesis at the end of the error message.
The following fixes will resolve most update and installation errors with Steam.
In other words, my computer BSOD'd while Steam was sitting there running in the background in the System Notification Area.