OWA works well both internally and externally with exception of externally uploading attachments > 200k these will timeout or hang. Files < 200k take 45 seconds to upload/attach but will attach. No errors in windows events or httperr1.log for OWA.
Exchange 2003 Front end to Back end scenario. Attachments allowed and not filtered. Forms-based authentication w/ wild card SSL. Front end exchange behind a firewall (all filtering and port blocking was disabled for test). Using multiple external workstations with Windows XP IE 7 and Firefox 2.0 with consistent results.
1. Deleted then recreated OWA virtual directories and metabase file
2. Allowed complete pass-through traffic for test workstation to server at firewall.
3. Patched front end server with windows updates and rebooted
4. Restarted services on back end server
5. Tried different browsers
6. Used Microsoft Network Monitor on test workstation (didn't know what to look for)
7. Double checked antivirus exceptions as per Microsoft recommendations