Samsung r530 laptop goes back to log on screen if left idle for a few minutes

That sounds like a failed hard drive. Nothing to do with the update.. just bad timing.

see my solution posted on other question

Here is an article on how to reset the password so that you can get onto the laptop

http://www.fixya.com/support/r10255556-reseting_password_windows_xp_or_windows

Try using the laptop without the battery and observe.
Following the link below for instructions on how to remove the battery on this laptop.
Samsung Series R530

Try hooking a external monitor to your video output, if flickering is gone suspect intermittent problem with LCD, or ribbon connector, if problem shows on both screens you may have a virus and a re-install would be required of your operational system, or you may have a hardware issue. Now you mentioned you had the item for a week, if it is new it should be under warranty, at least you can do a few basic checks.

check the power setting / hybernate under Control panel

Press FN F5

right click goto properties screen saver tab uncheck on resume password protect. thats xp dont remember if its different for vista or 7.

You may have loose screen interface connector on the back of the screen or on the mother board.
Check out www.insidemylaptop.com

What about the screen saver