Arturo
You need to check the following;
Go to Control Panel and double click Power Options.
In Power Options, click on the Advanced tab.
On the Advanced page, remove the check mark from the box next to "Prompt for
password when computer resumes from standby".
Click OK.
Put you computer into Standby mode and see if the problem is fixed.
Note: You may also want to launch the Display applet in Control Panel. Click
on the Screen Save tab and make sure "On resume, password protect" is
unchecked.
Good luck
Nepatsfan