Microsoft just published my article titled Investigating Issues with InfoPath 2010 SharePoint Applications. This article is broken up into two main sections:

  1. Debugging a Form Template — This section examines different ways to discover issues in a form template, using the InfoPath designer or Visual Studio (for custom code applications).
  2. Diagnostic Tools — This section reviews the most common tools for diagnosing issues with a form template or the run-time experience on the SharePoint server.

Many of the principles described in this article will work for InfoPath 2007 SharePoint applications as well.