Numeric keypad on W540 not working

Question

I might have seen the numeric keypad keys work once since getting this machine, but now can't get the keys to produce numbers.  Some of the keys initiate other actions not associated with numeric data entry.  
I tried removing the wireless dongle for my Microsoft wireless mouse but no improvement  --  I simply swapped this MS mouse from my old W510 without doing any formal install.  
This doesn't appear to be a hardware problem since the keypad keys have some effect  --  just not the intended effect.  Any suggestions would be greatly appreciated - thanks.  
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Answer 1

This is obviously not a subject that inspires much response either on the Lenovo community or on the Microsoft community.  
It turns out that the numlock on the real keyboard and the numlock on the OSK are linked  --  either one can turn the other one off or on.  Two times today, I had the real numpad keys actually working properly after first using the OSK numpad to enter a series of numbers  --  this was apparently a catalyst to get the real numpad working.  But only briefly.  After toggling the numlock once, then back, the numpad keys once again went dead.  The second time I had the numpad working, I left the numlock key alone, but rebooted the computer, only to lose numpad functionality again.  
I tried using the MS Keyboard Diagnostics (mskey.exe).  This utility shows that when the numpad keys have gone dead, they are really dead  --  nothing at all registers in the Raw Keyboard Input window when the numpad keys are pressed. But as soon as I deactivate numlock, then the Raw Keyboard Input shows the Home, left arrow, right arrow, etc. keys registering properly in the Raw Keyboard Input window.  (These are the alternate functions of the numpad keys.)  
The OSK numpad works, even the Lenovo technician in Atlanta was able to use my numpad remotely, but it's practically impossible to make the real numpad on the real keyboard work.  Didn't see anything in the BIOS that might help.  It still seems suspicious that the keyboard for this computer is shown as a Standard PS/2 Keyboard in the Device Manager, with a driver that Microsoft proclaims as being "up to date" for this machine dated dated 6/21/2006.