Strange click problem

I'm having this problem intermittently and quite often. Say when using chrome browser to right click save image:

1. I right click and the menu pop up
2. Mouse over Save Image As, then Left Mouse Down.

Now here is the problem, I often have to click a few times on the menu before the event fired. Else it is just sitting duck. Something like blank click point.

This happens on windows explorer too, say to right click file menu.

Does anybody has this problem? Is the problem lies on thinkpad or windows? It happens to my both system, t61 (vistabiz) and x200 (win7ultim). The same result with using external mouse or built-in mouse.