ok Guys. The problem appears to be solved now. Someone suggested me to disable all the plugins and enable the plugin one by one to see which one is creating problems. However, this exercise only resulted in confirming that the plugin installed at last made the plugins list disappear.
A very kind friend at #wordpress channel suggested me to increase the php memory limit. I asked my hosting people to increase the php memory limit to 64MB and as soon as they changed the configuration the plugins list came back, I installed a few more plugins to make sure it’s working and everything went well.
To increase php memory limit you have to increase the memory_limit option in /etc/php.ini.
Thanks to one and all who helped me.
Syedk