I was working on Drupal 6. I had to troubleshoot a site that has a problem in its link. The ugly URL looks like this: http://rcportblair.ignou.ac.in/admin/build/employee/search/result/none/0/none/%252F1
The last argument in the link i.e. %252F is a forward slash automatically added by the Drupal engine which was creating problem while generating result. There are many ways to handle these urls. One way is listed below:
<VirtualHost *:80> AllowEncodedSlashes On </VirtualHost>
This directive may be set in server config file (e.g. httpd.conf OR /etc/apache2/sites-available/default) and may appear inside <VirtualHost> containers to affect certain websites. Using it in .htaccess files is not allowed.