Thanks for the prompt reply.
Marko, I have started nfslock. I had disabled it recently 'cause I read that it's needed only in networking environments. Mine is a standalone laptop so I thought it'd be ok if I turn it off. Let's see if turning it on makes some effect.
dd_wizard, here's the output of top 3 CPU consuming processes that I found using top
1328 root 20 0 80120 40m 10m R 38.2 2.1 21:45.05 Xorg
2336 dharmit 20 0 43140 16m 13m S 17.4 0.8 9:59.57 gnome-system-mo
2667 dharmit 20 0 233m 66m 22m S 7.2 3.4 1:03.47 firefox
Firefox consumes 7.2% CPU. Are the other 2 processes consuming what they should consume, or is it more than what they should be using? I am not sure about it.