Symptoms

When trying to download a pdf document from an https address in IE8, the following error message is seen:

The file could not be written to the cache

Cause

This issue occurs if the server sends a "Cache-control:no-store" header or sends a "Cache-control:no-cache" header.  For further information, please review the following Microsoft article http://support.microsoft.com/kb/323308/en-us

Resolution

To resolve this issue in Internet Explorer 7 and in Internet Explorer 8, follow these steps:

1. Start the Registry Editor.
2. For a per-user setting, locate the following registry key:
   HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings
   For a per-computer setting, locate the following registry key:
   HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings
3. On the Edit menu, select Add Value.
4. To override the directive for HTTPS connections, add the following registry value:
   "BypassSSLNoCacheCheck"=Dword:00000001
   To override the directive for HTTP connections, add the following registry value:
   "BypassHTTPNoCacheCheck"=Dword:00000001
5. Quit the Registry Editor.
6. Ensure SSL is set correctly as outlined by this documentation: Running Confluence Over SSL or HTTPS