UI is slow to point of being unusable after long absence

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http://askubuntu.com – I leave my working PC powered and online when I leave office and it locks itself after some time and turns display off. None of other suspend features are active. When I get back at morning, it takes around 20 seconds for display to power on and more than minute or few for unlock password prompt to appear. After this, most often I simply give up and hard reset after 10 minutes of waiting for rest of UI to load up - nothing appears on screen except wallpaper. Yes, I run some memory hogs - like Firefox, Chrome and Komodo Edit, all with dozens of open tabs, but this is never a problem if I leave (HowTos)