Hi,
I recently updated from gf1.5beta1 to the final release of gf1.5 - this was a few days ago, and I regret to say that I did not check the form immediately after upgrading. Today I realized that the sections that were previously 2 and 3 column layouts using the the css ready classes were now staggered rather than side by side. I have been working on the site since then, so I can't be sure it was the update that messed up the formatting. That said, it seems like the most likely place to start looking for the problem.
I am also using the Thesis Theme, and I know that you removed Thesis specific .css from the core gf styles in this release. I did paste the Thesis Specific code from your blog post into my custom css file, but it didn't solve the problem.
Here is a screen shot of the form in pristine condition:
http://bluventureinvestors.com/wp-content/uploads/2011/04/Form-Appearance-Before.jpg
Here is the url of the live form with errors:
http://bluventureinvestors.com/submit-a-plan/
Thanks for your help.
Chris