When typing "G" and "H" rapidly together I get a "9"... "Z" and "X" make a "3" as seen below.
 
Anyone else have this issue?
 
df
fg
g9h  <---
hj
jk
kl
l;
zx3  <---
xc
cv
 

Weird.  I have not encountered this particular manifestation, BUT......other odd keyboard behaviors did show up for a while.  As an example, when trying to enter project notes many keystrokes would not be accepted and others would result in multiple characters of the key that was just clicked.  Obviously this made things a bit tedious.  Strangely enough I have not had this problem lately (maybe since after my X3 upgrade?.....not sure).  At any rate, I hope that I have not just jinxed myself by reporting this!  I'm sure that this post won't be of any help to you, but thought that you might like to hear that at least one other user has encountered some very strange keyboard behavior.

 
I thought this was a report of paranormal activity, especially given the mysterious x3 that appears.
 
If it isn't, where is this happening ?  In Sonar ?  In notepad ?
 

In my case it happened inside SONAR (e.g.-trying to add project notes in the Project Info dialog, or naming projects, etc.).  At first I thought that it was a PEBCAK problem (problem existing between chair and keyboard) but I quickly came to realize that it wasn't me!)

My 1-1/2 yr old laptop started doing this about 6 months ago and does it everywhere and all the time whenever I type fast. If I type slowly it won't happen so it's a glitch in the keyboard itself, I reckon.

Soens.... might be true in your case with the laptop but I swapped out three different keyboards and it did the same thing on every one of them.  Also reinstalled the keyboard drivers to make sure that there wasn't a problem there.  Strange......