I'm not sure if this has been mentioned before, but I ran across this while poking around with Kryptos. On the left side I have formed what I think is the "original matrix." On the right is part of the "tableaux." On the left I highlighted the first 2 typos: K-->Q in IQLUSION and R-->U in UNDERGRUUND. On the right I highlighted what the typos decrypt to. Curious that they are the same distance apart.

Assumptions and my guess at their likelihood:

1. The J in K1 belongs on line 1, as indicated by an arrow in Sanborn's worksheet, 75%
2. The I should be to the left of line 5 as seen in the worksheet, 99%
3. The first typo was intentional, and it's position and contents matter: 1%
4. Same for second typo: 50%