Why is it that my system dies when multitasking(it is happening from 11.10) on Ubuntu11.10(Unity), Kubuntu 11.10(KDE) and Deepin Linux which is based on 11.10(Gnome-Shell) The thing is that I thought with 12.04 I would get performance like I used to get on 11.04 on which everything used to run fine without any lag or hiccups.

The same lagging(Browser starts to stutter, increased delay in the launching of dash and applications)is happening on 12.04 http://i.imgur.com/YChKB.png and http://i.imgur.com/uyXLA.png . I believe that my system configuration is sufficient for running Ubuntu as you can check here http://paste.ubuntu.com/929734/ .

I had the Google voice and chat plugin installed on 12.04 so someone suggested that I should remove that and see if the performance improves but no such respite(I am having this on multiple operating system based on Ubuntu 11.10 as I have mentioned above). On a friends suggestion Ran Memory Test through Partition Magic and my system passed that fine.

One thing more that I would like to know is that why when I have 2Gb Ram and 2.1GB swap does my system starts lag and run poorly when Ram consumption goes 500+.
If you require anymore information I will gladly provide it.