Few months back i found that the "Home", "End" function keys are not working. Neither "F2" which I use for editing the excel renaming files stopped working.
I tried a lot on fixing the keyboard by re-installing drivers etc. Today, I did a quick search and found that a combination of "CAPS + Fn" locks the Function keys.
It appears that when I was cleaning my keyboard few months back, I seems to have accidently locked the keys. Since there was no tool tip available, I had to struggle a lot. I hope this post will be helpful for other users.