I learnt the meaning of Debian Sid's status of "Unstable" in the last two days. I have never had a problem with using Sid on my system except small hicupps for which I just had to hold some packages for a few days. But day before yesterday, after doing an update I saw an error for the package exim4-daemon-light. It didn't seem like a big problem as I just completed the update process and started using my machine.
Later that night, I had to reboot the machine to do some updates on WindowsXP. Little did I know what was in store for me! After doing the windows updates, I rebooted in Debian. And before it could get X running, I got the same error for exim4-daemon-light. I couldn't do anything at that time. Even CTRL+C wouldn't work! I tried to reboot again and in a different kernel, but luck wasn't on my side.
On further search I found out that exim4 was a mail-transport-agent and upon my repeated tried couldn't finish the configuration and boot my machine. I worked on it even yesterday and didn't get a step ahead of where I was a day earlier.
Finally, I removed some packages and then removed exim4-daemon-light. So as my mail-transport-agent (exim4) was removed, I had to install another one - exim. Its not even supported now, but I thought why not, it will be just for a while till I can get the error with exim4-daemon-light sorted out.
So right now, my machine has booted into the GUI mode after almost two days! Phew...now I understand why they call Debian Sid as unstable.
PS: Sorry to those who were accessing the webserver I run. The above problem was the cause of the downtime. Its up and running now.