Windows 7

Were there any changes made on the computer prior to the issue?

Method 1:

I would suggest you to refer to the link and re-enable the option to require a password on wakeup and check if it helps:

How do I change the password requirement when my computer wakes from sleep?

http://windows.microsoft.com/en-US/windows7/How-do-I-change-the-password-requirement-when-my-computer-wakes-from-sleep

Method 2:

I would suggest you to create a new user account and check if the issue persists.

Create a user profile.

http://windows.microsoft.com/en-US/windows7/Create-a-user-account

If the new user profile resolves the issue, you can fix the corrupt profile.

Refer:

Fix a corrupted user profile

http://windows.microsoft.com/en-US/Windows7/Fix-a-corrupted-user-profile

Check the Screen Saver options.

Right click the Desktop and select Personalize. At the bottom of the window, click the Screen Saver icon.

Check to make sure that the On resume display the logon screen option is not selected. If it is, remove the check mark from that option and select Apply/OK.

Even if a Screen Saver is not enabled, that resume option will force the system to go to the logon screen at the selected time interval.

Let us know what you find.

1)   Have you made any recent changes prior to this issue?

2)   What kind of browser are you using (Internet Explorer, Firefox, chrome etc…)?

3)   What is the make and model of the printer?

Follow the below mentioned steps which may help you in fixing the issue.

a)    Click Start

b)   Right click on Computer, and select Properties.

c)    Click on Advanced System Settings, click the Advanced Tab

d)   In the Performance section, click Settings

e)    Select the "Data Execution Protection" tab, and then click the 'Turn on DEP for all programs and services except those I select' option.

f)    Click the Add button, and then browse to C:\Windows\System32\dllhost.exe

g)   Click open, click OK on the warning message.

h)   Click Apply/OK.

Check if the issue still persists.

Please edit that shortcut - replace the initial 'http' with 'hxxp' - this will stop people accidentally clicking on it.

It does sound like you still have an infection, or your homepage has been hijacked.

Open Internet Options, and click on the Advanced tab - click on the 'Restore advanced Settings' button, and click on Apply

Click on the Security tab, and click on the 'Reset all Zones' button - click Apply

Click on the General tab, then the 'Use default' button - click Apply

Click OK

Restart Internet Explorer - what happens now?

If you still get strange sites up, check your settings in the Connections tab - most times, there should be nothing set there at all. and the LAN settings (and Proxy server) should be blank.

Then open an Elevated Command Prompt window, and type the following command

NETSH WINSOCK RESET

reboot on request - test Internet Explorer again.

Try this;

1) Click Start

2) Type Run

3) Copy and Paste C:\WINDOWS\system32\rundll32.exe shell32.dll,Control_RunDLL hotplug.dll  in the edit
field in Run
4) A press of the Enter Key should bring up the Safely Remove Hardware Dialog.

There is another thread discussing this issue - Torkin_Darkflight seems to have done a lot of experiments, has some interesting and suspicious findings but no firm conclusion. What I get from this thread is that even if you replace the corrupted file it will just become corrupt again:

http://forums.g4tv.com/showthread.php?t=145440&page=2