If you still want to block using a custom IPS rule, I noticed one immediate problem in the screen shots you posted. When you edit the signature (the small pop-up window) there is a section called Content and beneath that a section called Applications. According to the online help you must select (enable) the application that will trigger on this rule. In your screen shot there is nothing selected (enabled).
The other thing to check is over on the Clients screen. Select the group you want to apply the custom IPS rule to, then click on the Policies tab. Near the top, in the section called Location-independent Policies and Settings, you should see a link for Custom Intrusion Prevention. In there you have to enable your custom IPS rule.
Last but not least, after enabling everything on the management server don't forget to do an update on the client so that it pulls down the latest policy before you test.
Hope this helps,
Fred