We are having an issue with some PDF files not opening properly in IE8 with Adobe Reader 9 and 10. The issue is only affecting systems with the Windows 2003 Server OS. Systems with XP or Windows 7 are not affected. The symptom is that some PDF files open properly the first time in a new browser window, but other files show only a new browser window that is empty. If we then select the address of the file in the browser address bar and hit the enter key the PDF contents appear normally. We have several systems exhibiting the same behavior and can't find the cause or a solution. Any ideas?