Mac OS: Shutdown Warning Appears At Every Startup

Every time I start my conputer I get the improper shutdown message for a brief moment on the screen. I shutdown the computer using the power key, but the message says I didn't. Why is this?
The message about improper shutdown is activated by an invisible file named Shutdown Check. The file may be corrupt, causing the message to appear each time you start up the computer. The Shutdown Check file regenerates if removed from the hard disk, similar to a preference file. Try this to eliminate the errant message:


For more information on the Shutdown Check file and its function, please see the following Knowledge Base article:

Article 18011: "System 7.5: Improper Shutdown Notification"
Published Date: Feb 18, 2012