help

I Iam using Kaspersky Antivirus 2009. Whenever I scan the system using the Antivirus & leave the system idle for sometime, suddenly all the desktop Icons disappear & I can only see my desktop background & after 20 seconds later the screen turns to Blue. Then I can see my user name & password. As I click my user name & password, It takes long time to go the desktop & also all the Icons flickers vigoursly. However this does not happen when I switch on the computer.