Using Moodle 2.0 (Build: 20101130):
When creating URL resource with Display description option checked I'm getting two different results.
If external url is an url with .html reference (ie. www.example.com/url/page.html), when user click on URL resource description is shown and user can then open the external url.
If external url is an url with .php reference (ie. www.example.com/url/page.php) or no page is given (ie. www.example.com/url/): when user go to URL resource, no description is shown and user is redirected to external url.
There is diference in html code for these two type of url resource. The first one, with .html reference, has just href parameter in a tag. The second one, with .php or no page, has an onclick parameter in a tag (ie. <a onclick="window.location.href ='www.example.com/moodle/mod/url/view.php?id=1593&redirect=1';return false;")
