Hmmm. Strange. I just opened that same file in Tableau Reader, and the zip code data placement looks more correct. In Tableau 7 it does not...
Thanks for posting that, cause I was looking at this, and couldn't figure out what was wrong.
Which version of Tableau 7 are you using? On 7.0.8 the zips all look pretty accurate to me, though the circle and Zip Code Label of Lancaster CA 93536 could be better positioned vis-a-vis one another.