Password Issue

[MBP13]

Here's the problem: I have a password set on my 2010 MacBook Pro 13 so that I must enter it in once the computer is opened after being closed or awoken after sleeping. However, here's the problem. Sometimes, the password box will pop up, and I can hit "cancel", the password box will go away, and I will be allowed access to the desktop. Yet, other times I must enter in my password, and if I hit cancel, the box will just reappear again. The purpose of the password seems defeated if clicking cancel will allow access to my Mac without needing a password.

I'm running Snow Leopard 10.6.7.

Thanks for your help.