It might be worth checking what function they are trying to perform. I had the same problem when people were submitting changes to some of there personal information by the web. I removed some functionality which simply displayed there username on the confirmation screen, and the error disappeared.
Otherwise, in the server document in the Corporate Name & Address Book, try the following settings:
under tab basics 'maximum formula exccution time;
under internet protocols, DNS lookup cache found timeout:
under internet protocols, DNS lookup cache not found timeout:
under the same tab, the ‘Timeouts’ section which includes any of the following fields:
Persistent connection timeout:
Request timeout:
Input timeout:
Output timeout:
CGI timeout:
Hope this gives you a good starting point at least…
Sorry not sure which ones as I develop rather than administrate notes databases…
I had this problem and I changed the character set in header field to enable, find this in your server doc, within internet protocols then domino web engine.hope this helps