I have a strange issue in WSS 3.0. It uses forms-based authentication and is under ISA. I can check out any file except PDF files. When I check out a PDF I get "Value does not fall within the expected range." I suspect this has something to do with ISA and where SSL is terminated. I have had problems before where links that should be https were showing up as http in the site.
For the present issue I have tried various AAM settings and nothing seems to make any difference at all in the operation of the site.