There can be a some issues with ShortURLs on some webhosts; basically it requires that the "AcceptPathInfo" directive in Apache2 to be enabled, which isn't on some webhosts.

On some webhosts, they allow you the ability to make small configuration changes to your webspace through a .HTAccess file. Changes made in the ".HTAccess" file have a permission set for each option specified, you can generally find information on them through the Apache2 manual (the one we'll be working with is listed above (AcceptPathInfo)).

On the directive page, theres a section mentioning "Override" for each directive, which in this case is FileInfo. Your webhost will have to make an update to your site add add either the line "AcceptPathInfo On" or "AllowOverride FileInfo". The first will turn it on globally for your site (as it should be) or they can choose to allow you to enable it where you want to with the later.

Please note that, in some cases, they will already allow you to make changes to the .htaccess file, so it'd be good to test it (if it isn't enabled, it just will fail to work, as it already does).

If they choose the later, then you can make the update in your .htaccess file by adding this line: AcceptPathInfo On