drupal 6

We are currently experimenting with using Drupal 6 (soon Drupal 7) with ASP.Net Forms Authentication and a mildly modified External HTTP Authentication Module. Everything is working great for authenticated users. For anonymous requests everything works well too, with one exception. All PHP Posts by unauthenticated visitors hang until the PHP Timeout and then return a 500.0 Error. This error provides no detail of the actual description of the problem even though verbose logging is on. This is true inside or outside of Drupal.