Analysis, SHOW has "SQL SERVER" greyed out, cannot monitor

[beachldy]

In trying to monitor a SQL Server, I can get all statistics EXCEPT for those listed in the listbox below "SQL SERVER", such as User Connections, SQL Server Processor Time, etc.

Why can't I get these statistics working? When I select something like "User Connections", I get an error "No data available between 18 Jul 2012 09:59 and now".....which further is explained by this:
Data may be missing for part of the time range for any of the following reasons:

•SQL Monitor was not running
•The monitored object was unavailable or suspended
•Older data has been purged