By god's grace, my n900 is working fine without issues as of now. (it may show probelms in the next moment )

I did the following :

1. Fully charged the phone
2. Switched off it and kept is in a dry pace for 3-4 days
3. Turned on the phone and removed the "Switch off" menu item from the "power button menu". This is possible by Modifying the "systemui.xml" file in the "/ect/systemui/" folder.