In cgi/fastcgi mode, the search form target is of the form http://myserver/somedir/index.php?/siteaccess/content/search

The problem is that when the browser sends the form contents to the server, it strips the path_info from the url and replaces it with a simple query string:
http://myserver/somedir/index.php?search=text

This breaks the navigation, as a different siteaccess will be used...

As a tip, using IIS+FASTCGI, the http://myserver/somedir/index.php/siteaccess/module/view url is supported correctly by IIS (at least version 6) and php; this means that there would be no need to fix this bug in the html form and/or module, but simply to use urls without the question mark.

The problem lies with ezsys, that insists upon adding '?' in the query string.
If otoh we force useVirtualHost, ezsys strips out not only '?' but also 'index.php' - there's no winning solution here... (unless a rewrite module is used...)