keyboard - Right shift key not working with " key

I am facing an unusual problem with my laptop's keyboard.

_{Please read carefully, as this might sound a little confusing.}

My ' (single quote) key seems to be working just fine; my right Shift key is also (mostly) working.
But when I try to use use the right Shift key along with ' key to produce a " (double quote), it doesn't work.

To get a ", I have to press left Shift+'.

All the keys seem to be working just fine except the combination of these two. I don't understand why.

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EDIT 1: When I press right Shift+' key, nothing appears on the screen. Again nothing happens when I press right Shift+' twice. Nothing appears on the screen later on.

I am using Windows 7.

This problem didn't occur earlier. One fine morning, my keyboard had stopped working. Just stopped working, I don't know why. So I shut it down. Two hours later, it started working again on its own. The problem has started since then.

EDIT 2: Okay, now another key combination is also not working, i.e. the same problem is occurring with the left Shift and the + key.

So my

1. right Shift along with '


2. left Shift along with +

are not working. Can't seem to understand why.